Some standard content:
ICS31.180
National Standard of the People's Republic of China
GB/T4588.3—2002
eqyIEC60326-3：1991
Design and use of printed boards
Design and use of printed boards2002-11-25Promulgated
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
Implementation on April 1, 2003
GB/T4588.32002
Cited Standards
3 Materials and surface plating (coating) layers
3.1 Materials
3.2 Metallic coatings
Non-metallic 5.1 Reference datum 5.2 Dimensions of printed board 5.3 Thickness of printed board Dimensions of holes Dimensions of slots and notches, Dimensions of conductors Dimensional stability Electrical properties Resistance Current carrying capacity Insulation resistance 6 .4 Withstand voltage
6.5 Other electrical properties·
Mechanical properties·
7.1 Adhesion of conductive patterns
7.2 Warpage
8 Other properties
8.1 Welding...
8.2 Delamination
8.3 Flame retardancy
Packaging·
Overview·
Packaging materials:
Packaging steps
Appendix A (Appendix to the standard) Determine the size of the clearance window of the permanent protective coating 11
GB/T4588.3-2002
This standard is equivalent to the second edition of the International Electrotechnical Commission IEC60326-3:1991 "Printed boards Part 3: Design and use of printed boards", and is a revision of the national standard GB/T4588.3-1988≤Printed circuit board design and use". Its technical content and compilation principles are equivalent to those of the standard.
This standard specifies the design specifications and use requirements of printed boards, and plays a guiding role for designers and users of printed boards. The documents cited and the technical parameters specified in the standard are suitable for adoption in my country. The main technical difference between this standard and the adopted international standard IEC60326-3:1991 is that, based on the importance of electrical performance in design and use, in order to make this standard more perfect, "characteristic impedance", "inductance and capacitance" and other contents are added to the electrical performance part.
This standard basically covers the main contents of the original national standard GB/T4588.3-1988. There are some differences in its technical content, mainly adding the functions, scope of use, shape of clearance window and relevant dimensions of flexible printed boards and rigid-flexible printed boards for copper-clad substrates, adhesives, cover substrates and cover layers for flexible printed boards, as well as the contents of flame retardancy tests. Appendix A of this standard is the appendix of the standard.
This standard is proposed by the Ministry of Information Industry of the People's Republic of China. This standard is under the jurisdiction of the National Technical Committee for Printed Circuit Standardization. This standard was drafted by the 15th Electronic Research Institute of the Ministry of Information Industry. The main drafters of this standard are Yi Jing, Wang Fang, Zhang Chunting and Liu Yun. 1 Scope
National Standard of the People's Republic of China
Design and use of printed boards
Design and use of printed boards This standard deals with the design and use of printed boards, but has nothing to do with the manufacturing method. GB/T4588.3—2002
eqvIEC60326-3:1991
Synonym GB/T4588,3—1988
This standard provides suggestions for the design and use of printed boards to designers and users of printed boards. 2 Referenced Standards
The provisions included in the following standards constitute the provisions of this standard through reference in this standard. When this standard was published, the versions shown were valid. All standards are subject to revision, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T1360-1998 Printed circuit grid system (idtIEC97:1991) GB/T2036—1994
Printed circuit terminology (neqIEC194:1988) GB/T4677—2002
GB/T 4721-1992
GB/T4722—1992
GB/T 4723—1992
Test methods for printed boards (eqvIEC60326-2:1990) General rules for copper-clad laminates for printed circuits (negIEC249:1985~1988) Test methods for copper-clad laminates for printed circuits (neqIEC249-1:1982) Copper-clad phenolic paper laminates for printed circuits (negIEC249-2:1985~1988) GB/T12629—1990F
Thin copper-clad epoxy glass cloth laminates with limited flammability (for the manufacture of multilayer printed boards) (eqvI GB/T13555—1992
GB/T13556—1992
GB/T13557—1992
Flexible copper-clad polyimide film for printed circuits (eqvIEC249-2-13:1987)Flexible copper-clad polyester film for printed circuits (eqvIEC249-2-8:1987)Test methods for flexible copper-clad materials for printed circuits (eqvIEC249-1:1982)Double copper-clad polyester film with limited flammability for printed circuits Polyimide glass cloth laminate GB/T16315-1996
(neqIEC249-2.1993)
GB/T16317—1996 Thin double copper foil polyimide glass cloth laminate with limited flammability for multilayer printed circuits (negIEC249-2:1992)
GJB1438—1992 General specification for printed circuit connectors and accessories GJB2142—1994 General specification for metal foil laminates for printed circuits SJ/Z9130—1987 Printed circuit boards
3 Materials and surfaces 3.1 Materials
3.1.1 General
When selecting suitable materials, the designer of the printed board should consider: a) the manufacturing process used (such as subtractive method, additive method, semi-additive method); b) the type of printed board (such as single-sided board, double-sided board, multi-layer board, rigid printed board, flexible printed board and rigid printed board); c) electrical energy:
Approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on November 25, 2002 and implemented on April 1, 2003
d) mechanical properties;
GB/T4588.3—2002
e) Special properties, such as flame retardancy and combustion characteristics, machinability, flexibility, etc. The process used determines whether a metal foil substrate should be used (subtractive process) or a bimetal foil substrate should not be used (additive or semi-additive process). Therefore, the materials of the printed circuit board are: a) Copper foil synthetic resin bonding sheet or copper foil polymer film, which can be used to selectively remove unnecessary parts of the conductive foil to obtain a conductive pattern.
b) Uncopper foil synthetic resin bonding sheet or polymer film, which can selectively deposit conductive materials on uncopper foil substrates to obtain conductive patterns.
Table 1 provides the basis for qualitative selection of printed circuit board materials. The table does not cover all materials, only some commonly used materials are provided. Table 1 Guide to the Selection of Substrates for Printed Boards
Rigid Printed Boards
Mechanical Properties
Electrical Properties
High Temperature Resistance
Moisture Resistance
Soldering + Humidity Resistance
Phenolic Paper
Laminate
Epoxy Paper
Laminate
There is currently insufficient data to fill in this column. - May cause problems under certain conditions. Polyester Glass
Felt Laminate
"O" - Moderate, usually no problem in most applications, *+\\++n+++\
"NA" Not Applicable.
Good, Very Good, Excellent
Epoxy Glass
Cloth Laminate
Flexible Printed Board
Polyimide
Ethylene Propylene Oxide
Film (FEP)
Material that complies with national standards should be used preferentially. The standard for copper-clad printed board substrates contains specifications for rigid and flexible double copper foil substrates and adhesive sheet materials used in the manufacture of multilayer printed boards. If there is no recognized specification that is compatible with the required material, a detailed specification that is compatible with the material should be prepared. Priority should be given to:
a) using the test methods of GB/T4722 and GB/T13557, b) following the structure and format of the standard for copper-clad printed board substrates: c) cooperating with the material supplier.
If special properties are important, they should be determined and specified together with the material supplier. 3.1.2 General Notes on Materials for Printed Boards
The maximum operating temperatures quoted in the following notes are intended as a guide only and do not imply a dramatic change in performance or rate of aging if these temperatures are exceeded.
In addition, it should be noted that the properties of some materials are affected by factors such as board design (e.g., board thickness, amount and distribution of metal, number of layers, solder resist, etc.) and manufacturing processes (e.g., lamination processes for multilayer boards), resulting in the performance of the processed boards being found to be quite different from that of the raw materials. 3.1.2.1 Copper-clad Substrate Phenolic Paper Laminate for Rigid Printed Boards
This material is available in different grades. Most grades are capable of use up to approximately 70°C-105°C, although prolonged operation above this temperature range may result in some degradation of performance, depending on the grade and thickness of the material. However, overheating 2
GB/T4588.3-—2002
can cause carbonization, and in this affected area, the insulation resistance may drop to very low values. Factors that produce such heat sources include heating resistors.
In the normal temperature range, the substrate may undergo severe deterioration, which is not caused by carbonization. Sunlight can also cause the substrate to deteriorate. In these cases, no changes in material properties will be caused. Placing in a high humidity environment will greatly reduce the insulation resistance of the substrate, but when the humidity drops to very low values, the insulation resistance will increase again.
Epoxy paper laminate
Compared with phenolic paper laminate, this material has corresponding improvements in electrical and non-electrical properties, including better machinability and mechanical properties. Depending on the thickness of the material, its operating temperature can reach 90℃~110℃. Polyester glass mat laminate
Most of the mechanical properties of this material are lower than those of glass cloth-based materials, but higher than those of paper-based materials. However, it has good impact resistance. It also has good electrical properties and can be used in a wide frequency range, even in high humidity environments. Its resistance to tracking and arcing depends on the grade of the material selected. Most grades have a service temperature of 100°C~105°C.
Ring-rolled glass cloth laminate
The mechanical properties of this material are higher than those of paper-based materials, especially the bending strength, impact resistance, dimensional stability of the X, Y, and B axes, warpage, and resistance to welding heat shock are better than those of paper-based materials. The electrical properties of this material are also very good. Most grades can be used at temperatures up to 130°C and are less affected by harsh environments (humidity). 3.1.2.2 Certain properties of copper-clad substrates for flexible printed circuit boards may change significantly due to the adhesive system used. When both flexible and rigid parts are included in the same printed board, the materials used for rigid printed boards (3.1.2.1), materials used for flexible printed boards (3.1.2.2) and materials used for multilayer printed boards (3.1.2.5) can be combined in the same structure. Polyester film
Flexibility is the characteristic of polyester film that is commonly used. It is characterized by the ability to form a retractable coil when heated. If a suitable adhesive is used, this material can be used in the range of 80℃ to 130℃, and the actual use temperature depends on the grade of the material. Special attention should be paid when welding, as this material is prone to softening and deformation at welding temperatures. It has excellent electrical properties and can still maintain its good electrical properties when exposed to high humidity environments. Polyimide film
This material has good flexibility and can be preheated to remove absorbed moisture to ensure safe welding. Generally, adhesive-bonded polyimide films can work continuously at temperatures up to 150℃. Special fusion-bonded polyimide films with fluorinated ethylene propylene (FEP) intermediate adhesive can be used at 250°C. Polyimide films without adhesives for special purposes can be used at higher temperatures. Polyimide has excellent electrical properties, but may be affected by absorbed moisture. Fluorinated ethylene propylene film (FEP)
This material is usually combined with polyimide or glass cloth to make a laminate, and has good flexibility and stability at a welding temperature not exceeding 250°C. It can also be used as a non-support material. Fluorinated ethylene propylene film is a thermoplastic material with a melting temperature of about 290°C. It has excellent moisture resistance, acid resistance, alkali resistance and organic solvent resistance. Its main disadvantage is that the conductive pattern is prone to movement at the lamination temperature during lamination.
3.1.2.3 Adhesives for flexible printed boards
Adhesives are used to bond the layers of double cover layers and flexible multilayer printed boards. They can be thermosetting or thermoplastic materials. The appropriate adhesive should be selected based on the compatibility with the bonded materials and the performance requirements of the flexible printed boards. The selection of the appropriate adhesive depends on the following factors: the type of flexible printed boards, through-connection requirements, bending requirements (static/dynamic), operating temperature, humidity, cost, etc.
GB/T4588.3—2002
3.1.2.4: Covering materials for flexible printed boards The cover layer of a flexible printed board is used to cover the surface conductors, thereby increasing and/or maintaining the electrical energy of the flexible printed board. The cover layer and adhesive system are the same as those used in the substrate. The appropriate cover layer should be selected based on the compatibility with the materials used and the performance requirements of the flexible printed board.
See 3.3.3.3 for the selection of cover material.
3.1.2.5 Materials for multilayer printed boards
Multilayer printed boards are composed of two or more layers of conductive patterns and insulating materials interlaced. It is composed of a single thin printed board (single-sided or double-sided) bonded together with insulating adhesive sheets. These adhesive sheets are composed of sheets (such as glass cloth impregnated with semi-cured resin), and when the multilayer printed boards are laminated, the resin is cured to the final stage. Copper foil epoxy glass cloth
The copper foil substrate used for a single thin printed board is basically the same as the substrate used for single-sided and double-sided printed boards. Generally, it is thinner than the materials used for single-sided and double-sided printed boards, and its thickness is standardized within several ranges, rather than a few fixed values. It also has the same basic properties as the above-mentioned related materials.
Epoxy impregnated glass cloth bonding sheet
This bonding sheet is composed of sheets (such as glass cloth impregnated with semi-cured resin), and the resin is cured to the final stage after the multi-layer printed board is laminated. Therefore, their final properties are only shown after lamination. However, it is worth noting that the production process and the design of the multi-layer printed board may have a considerable impact on the performance of the material. 3.1.2.6 Special and new materials
In addition to the materials already mentioned here, there are some special and new materials on the market that are not standardized. Note: An example of a special material is silicone glass cloth, which has a service temperature of up to 180°C. Due to the development of technology, it is not possible to give a general description of special and new materials here. If these materials are used, they should be negotiated with the material supplier.
3.1.3 Some special properties
3.1.3.1 Machinability
The material standard does not contain detailed descriptions of machinability. It only states that the laminate can be punched, sheared or drilled without delamination according to the manufacturer's recommendations. However, the machinability of different materials may be different, and some materials may even have different levels of machinability. For example, some materials can be punched at room temperature, while others can only be punched at elevated temperatures. It is therefore necessary to follow the material supplier's recommendations.
3.1.3.2 Flame retardancy
Some materials have a certain degree of flame retardancy. Flame retardancy can be divided into different levels. Detailed descriptions are given in the relevant specifications (e.g. GB/T12629, GB/T16315 and GB/T16317). It should be noted that the flame retardancy of the substrate given can only be used as a guide and may differ greatly from the flame retardancy of the processed printed board. The design of the printed board (e.g. the size of the printed board, the amount and distribution of the metal, the number of layers, etc.) has a great influence on the flame retardancy. Under normal circumstances, the flame retardancy of the printed board is better than that of the substrate alone, that is, the risk of fire will be lower. For details, see 8.3.3.2 Metal coating
Metal coating is used to protect the metal (copper) surface and ensure its solderability. It can also serve as an anti-corrosion layer for etching liquid in some processing processes (e.g. in the processing of plated holes). The metal coating can also serve as the contact surface between the connector and the printed board, or the bonding layer between the surface mount device and the printed board. 3.2.1 Materials
A coating suitable for the conductive pattern should be selected according to the purpose of the printed board. The type of surface plating directly affects the production process, production cost and the performance of the printed board, such as life, solderability and contact. The following are examples of widely used surface plating: a) Copper (no additional plating)
GB/T4588.3-2002
All printed boards without plating requirements use copper. Copper is usually used as a temporary protective coating. The recommended value of the copper plating thickness in the plated hole is given in 5.4.2.
b) Tin
Used to protect solderability. The thickness is usually 5μm~15μm. c) Tin-lead (electroplating or solder)
Used to protect solderability. Its thickness depends on the process used. When using electroplating, the thickness of the tin-lead plating is usually between 5μm and 25μm. The local thickness of the electroplated tin-lead after hot melting or the tin-lead applied by the solder tank or hot roller may be less than 1μm. These areas are mainly located in the transition zone between the connection pad and the hole wall. The solderability of the transition zone will be lower than that of other areas. The eutectic mixture of tin-lead with 63% tin and the rest lead has the lowest melting point. In fact, the acceptable composition content is 55%~75% tin and the rest is lead.
The solderability of tin-lead decreases with the extension of storage time. Excess electroplated tin-lead or material can be removed by spraying hot air or hot oil. However, it is worth noting that the dimensional characteristics of the printed board (such as warpage) may be affected by placing the printed board in a heat source (such as molten solder).
d) Gold
Gold is generally on a barrier layer (such as nickel) and is usually used for switches and printed plug contacts. The characteristics that must be considered for gold as a contact surface are: thickness, hardness, wear resistance, contact performance, etc., which depend on many factors (see 3.2.3 Key points for printed contact pieces). Sometimes gold plating is also required on non-contact conductive patterns. Special attention should be paid when these patterns are used for soldering. Soldering on gold may cause serious problems with solder joints and solder baths because gold and tin-lead alloy. e) Other platings
For example, palladium on nickel, gold on tin-nickel and gold on nickel are also used for printed contacts. The points for printed contacts given in 3.2.3 should be followed.
3.2.2 Adhesion, thickness, porosity
The adhesion and thickness of any plating on the conductive pattern can be checked by GB/T 4677 test 13a or 13b (adhesion) and test 13f (thickness). However, since the feasibility of porosity testing and the confidence in the conclusions are very limited, special attention should be paid when specifying porosity tests 13c, 13d and 13e. 3.2.3 Printed contacts
When using printed contacts, care should be taken to select a plating that is compatible with the plating on the matching corresponding contacts. Since the selection of a suitable coating is related to a number of factors, most of which are interrelated, there is no general rule to follow. For example: the corresponding type of coating;
the corresponding contact design (shape, contact pressure, etc.); durability, the expected number of uses;
electrical performance requirements (such as contact resistance); mechanical processing performance requirements (such as insertion and extraction force); environmental conditions of use.
The metal surface of the printed contact piece should be smooth and free of defects that can cause a decrease in electrical and mechanical properties. If necessary, it can be checked by visual inspection, see Test 1 of GB/T4677. When the local contact area is important, an inspection mask as shown in Figure 1 can be used.
3.3 Non-metallic coating
Non-metallic coating materials are used to protect printed boards. In addition, solder resists are used to prevent solder wetting of conductors in non-soldering areas. 3.3.1 Overview
When double-coated assemblies are exposed to high humidity conditions, improper cleaning may lead to reduced adhesion. Due to the reduction in adhesion, separation points or debris can be seen at the interface between the coating and the substrate, and peeling (powdering) can be seen. 5
GB/T4588.3—2002
Before applying any coating, it is most important to properly clean the printed board. If the printed board has organic or inorganic contamination, its insulation resistance cannot be improved by the coating.
If the coating is selected and used incorrectly, it may cause the printed board's flame retardancy, insulation resistance, and electrical performance under high frequency use to decrease.
3.3.2 Temporary protective coating
3.3.2.1 Temporary protective coating for solderability
Temporary protective coating can be used to protect the solderability of conductive patterns. Temporary protective coatings are usually used on conductive patterns that are not covered by a double layer of metal surface with good solderability (for example: bare copper) to maintain good solderability during the necessary time period.
Depending on the materials used, the temporary protective coating may be removed before soldering or may act as a flux. Temporary protective coatings that are not removed before double fluxing are resin-based and soluble in the flux solvent.
Printed board edge contact area
Printed board edge
Total contact width
Contact area inspection mask
Minimum area width; b-
Total contact width
Maximum area width.
Note: Unless otherwise specified, r = 0.25 mm (0.01 in) when the copper foil is 35 μm (0.0014 in). Figure 1 Example of contact area and inspection mask
Excessive drying and/or long-term storage, or excessive heating (for example, when the printed board is subjected to vapor phase soldering), may cause some resin-based coatings to solidify at a point where the coating is no longer fully dissolved in the short time between the application of flux and the soldering, thereby reducing the soldering effect.
The thickness of the resin-based coating is usually thinnest at the intersection of the hole wall and the connection land. Over time, the solderability of the plated hole may decrease faster than other areas.
For these reasons, the coating should be compatible with the process to be implemented. For example, drying, fluxing, soldering and hot-melt methods must be carefully considered.
3.3.2.2 Temporary solder resist
GB/T4588.3—2002
This coating is usually applied by screen printing before soldering, covering a specified area of the printed board to prevent the conductive pattern in this area from being wetted by solder.
For example: Temporary solder resist is applied to the circuit area with precious metals as a surface coating. In addition, this coating can also be used to protect certain areas from damage during the production process and storage. Temporary solder resist can be removed by peeling or soaking with a suitable solvent, depending on the type of solder resist used. It should be noted that temporary solder resist must be completely removed. 3.3.3 Permanent protective coating double layer
3.3.3.1 Overview
Permanent coatings can improve or maintain the electrical properties of printed boards, such as insulation resistance and breakdown voltage between conductors on the surface of the printed board. They usually contain strong scratch-resistant materials to protect the board surface from damage. In normal use, they are designed to remain permanently on the printed board.
Permanent protective coatings can improve or maintain the electrical properties of printed boards by: preventing moisture from entering the substrate;
preventing the deposition of dirt (e.g., moisture-absorbing dirt) between conductors;
acting as an insulating material between conductors;
acting as a protective layer inside or on the surface of plated-through holes (vias) that do not require soldering. 3.3.3.2 Permanent solder resist
This coating is applied before the soldering operation to cover the specified area of the printed board to prevent the conductive pattern in that area from being wetted by solder. It is different from peel-off or wash-off temporary solder resists. After the soldering operation, permanent solder resists cannot be removed, but serve as a permanent protective coating. When used solely as a solder resist, it should have adequate protective properties in addition to other essential properties. Solder resist may also be applied to the component side as a permanent protective coating, in which case it serves only as a permanent protective coating.
Solder resist may be used for one or more of the following reasons: a) To prevent solder wetting in specified areas;
b) To prevent bridging between adjacent conductive patterns; c) To promote and improve solderability by concentrating solder on portions of conductive patterns not covered by solder resist; d) To reduce solder consumption and solder tank contamination; e) To protect the printed board during processing;
( ) To improve or maintain the electrical properties of the printed board; g) To act as an insulating layer between the component body and the conductive pattern below it. Solder resist applied over conductive patterns that are easily molten during soldering may wrinkle, blister, or peel after soldering.
Selectively avoiding solder mask over solder or, for example, applying a thicker solder mask over solder (which also acts as a thermal barrier), using thinner solder layers, designing thin wires, and opening windows in large conductive patterns can reduce wrinkling, blistering, or peeling. If wrinkling, blistering, or peeling is unacceptable, a solution should be proposed for the change. There are two basic types of solder resists: printed, generally screen-printed, where the solder resist is printed on the specified printed board pattern; and photoimageable solder resist, where a special wet or dry film is applied to the printed board and exposed (usually to ultraviolet light) and developed to produce the corresponding pattern.
Screen printing is usually less expensive, but using photoimageable solder resists can achieve smaller tolerances (see 3.3.3.4). Misalignment between the solder mask clearance window and the land, as well as diameter deviations between the land and solder mask clearance window, may cause the land to be partially covered, reducing the soldering area. When necessary, the relevant specifications should specify appropriate size and overlap requirements. 3.3.3.3 Covering layer
The covering layer is an insulating protective layer covering the surface of the printed board. It is usually a film or insulating metal foil bonded to the surface of the flexible printed board with an adhesive. It can also be made on a rigid printed board by processes such as pre-molding materials and lamination. In addition to the clearance window for welding and contact, the covering layer covers the entire surface of the printed board. The cover layer of the flexible printed board covers the surface conductor to improve or maintain the electrical performance and flexibility of the printed board. The covering layer is usually 0.025 mm thick plus the thickness of the adhesive, and its size is unstable. It must be considered when determining the minimum ring width with sufficient pad area.
To protect the unsupported hole lands on flexible printed boards from lifting from the substrate surface, a toe can be added to such lands or a cover layer can be used to cover the land circumference, see Figure 2. 0.25mn
Residual window of cover layer
d—drilling hole diameter: D—
-Residual window diameter:
Minimum distance: y-
Figure 2 Methods for strengthening pads
Engagement width of short-term cover layer.
It is not practical to use a single cover layer clearance window in a dense solder joint area (such as a connector structure), so this window can be made into the structure shown in Figure 3. For unsupported holes, a toe should be added to the copper land. It is not appropriate to use a cover layer on a flexible printed board to cover the metal coating area that is easily melted during the soldering operation. The cover layer may wrinkle and/or blister after the soldering operation. Combined methodbZxz.net
Preferred
Acceptable
Strip window method
Figure 3 Preferred window shape
Single window method
Excerpt
Acceptable
GB/T4588.3—2002
1. The combined method and the single window method are the most expensive. The strip window method is prone to a weak point, that is, the copper and the substrate may crack here. 2. The single window method is used for flexible printed boards with low-density connection pads. 3. The strip window method or combined method is used for flexible printed boards with high-density connection pads. 4. The strip window method (bare wire) always requires additional coating of a certain coating or potting compound to provide more adhesion support for the bare wire after the part is assembled to the conductive pattern.
5. The combined method (bare wire) always requires additional coating of a certain coating or potting compound to provide more adhesion support for the bare wire after the part is assembled to the conductive pattern.
3.3.3.4 Tolerances and Design of Solder Mask Pattern or Covering The product design and final product requirements shall include process tolerances for the position and size of the solder mask or cover clearance window. A certain area (including size and position) not covered by the solder mask or cover is usually specified as the minimum effective soldering area (see Figure 4). When this area includes component soldering holes, the minimum value of the solderable ring width may replace the position and size tolerances with the agreement of both the supplier and the buyer.
Width of effective solder pad
Permanent protective coating
Thickness hole or non-plated hole
Effective surface soldering area
Minimum good ring width
Figure 4 The design width of the solder mask or double cover clearance window in the permanent protective coating shall be equal to the width of the minimum effective soldering area plus the process tolerance. When agreed by the manufacturer, the process tolerance is equal to the minimum tolerance PT1.
In many cases, the size of the double-coated opening depends on how much of the conductor closest to the pad needs to be covered. When the coating of such a conductor has specific requirements, the design width of the corresponding solder mask or double cover layer area should be equal to the width of the coated area plus the process tolerance, which is equal to the minimum tolerance PT2 if agreed by the printed board manufacturer. When only approximate values are required, PT1 and PT2 can be considered equal. Solder Mask Tolerance
The solder mask tolerance of epoxy glass cloth boards that have not been solder fused can refer to the following guidelines. For photo-imaging processes, the position tolerance can be 0.1mm to 0.6mm depending on the size of the product being imaged and the positioning method. For screen printing processes, the position tolerance can be 0.4mm to 1.0mm. Cover Layer Tolerance
For processes where the double cover layer is punched or drilled and then laminated, the process tolerance can be 0.5mm to 1.5mm. Appendix A lists an example of solder mask or cover layer. 3.3.4 Conformal Coatings
3.3.4.1 Overview
Conformal coatings are electrically insulating materials applied to printed boards or printed board assemblies to act as a protective barrier to the environment.2 Permanent solder resist
This coating is applied before the soldering operation to cover the specified area of the printed board to prevent the conductive pattern in the area from being wetted by solder. It is different from the temporary solder resist of the stripping type or washing type. After the soldering operation, the permanent solder resist cannot be removed, but acts as a permanent protective coating. When used only as a solder resist, it should have sufficient protective properties in addition to other necessary properties. Solder resist as a permanent protective coating can also be applied to the component side, in which case it only acts as a permanent protective coating.
Solder resist can be used for one or more of the following reasons: a) Prevent the specified area from being wetted by solder;
b) Prevent bridging between adjacent conductive patterns; c) Concentrate solder on the conductive pattern portion not covered by the solder resist, promote and improve solderability; d) Reduce solder consumption and solder tank contamination; e) Protect the printed board during processing;
() Improve or maintain the electrical performance of the printed board: g) Act as an insulating layer between the component body and the conductive pattern below it. If the material of the conductive pattern, such as solder, is easily molten during the soldering process, the solder resist applied over it may wrinkle, blister, or peel after soldering.
Selectively avoiding the application of solder resist over the solder or, for example, applying a thicker solder resist layer over the solder (which also acts as a thermal barrier), using thinner solder layers, designing thin wires, and opening windows in large conductive patterns can reduce wrinkling, blistering, or peeling. If wrinkling, blistering, or peeling is unacceptable, a solution should be proposed for change. There are two basic types of solder resists commonly used: printed types, generally screen printing, which is to print the solder resist on the specified printed board pattern; photoimageable solder resist, which is to apply a special wet or dry film on the printed board, and then produce the corresponding pattern after exposure (usually ultraviolet light) and development
Screen printing is usually less expensive, but using photoimageable solder resist can achieve tighter tolerances (see 3.3.3.4). Misalignment between the solder mask clearance window and the land, as well as diameter deviations between the land and solder mask clearance window, may cause the land to be partially covered, reducing the soldering area. When necessary, the relevant specifications should specify appropriate size and overlap requirements. 3.3.3.3 Covering layer
The covering layer is an insulating protective layer covering the surface of the printed board. It is usually a film or insulating metal foil bonded to the surface of the flexible printed board with an adhesive. It can also be made on a rigid printed board by processes such as pre-molding materials and lamination. In addition to the clearance window for welding and contact, the covering layer covers the entire surface of the printed board. The cover layer of the flexible printed board covers the surface conductor to improve or maintain the electrical performance and flexibility of the printed board. The covering layer is usually 0.025 mm thick plus the thickness of the adhesive, and its size is unstable. It must be considered when determining the minimum ring width with sufficient pad area.
To protect the unsupported hole lands on flexible printed boards from lifting from the substrate surface, a toe can be added to such lands or a cover layer can be used to cover the land circumference, see Figure 2. 0.25mn
Residual window of cover layer
d—drilling hole diameter: D—
-Residual window diameter:
Minimum distance: y-
Figure 2 Methods for strengthening pads
Engagement width of short-term cover layer.
It is not practical to use a single cover layer clearance window in a dense solder joint area (such as a connector structure), so this window can be made into the structure shown in Figure 3. For unsupported holes, a toe should be added to the copper land. It is not appropriate to use a cover layer on a flexible printed board to cover the metal coating area that is easily melted during the soldering operation. The cover layer may wrinkle and/or blister after the soldering operation. Combined method
Preferred
Acceptable
Strip window method
Figure 3 Preferred window shape
Single window method
Excerpt
Acceptable
GB/T4588.3—2002
1. The combined method and the single window method are the most expensive. The strip window method is prone to a weak point, that is, the copper and the substrate may crack here. 2. The single window method is used for flexible printed boards with low-density connection pads. 3. The strip window method or combined method is used for flexible printed boards with high-density connection pads. 4. The strip window method (bare wire) always requires additional coating of a certain coating or potting compound to provide more adhesion support for the bare wire after the part is assembled to the conductive pattern.
5. The combined method (bare wire) always requires additional coating of a certain coating or potting compound to provide more adhesion support for the bare wire after the part is assembled to the conductive pattern.
3.3.3.4 Tolerances and Design of Solder Mask Pattern or Covering The product design and final product requirements shall include process tolerances for the position and size of the solder mask or cover clearance window. A certain area (including size and position) not covered by the solder mask or cover is usually specified as the minimum effective soldering area (see Figure 4). When this area includes component soldering holes, the minimum value of the solderable ring width may replace the position and size tolerances with the agreement of both the supplier and the buyer.
Width of effective solder pad
Permanent protective coating
Thickness hole or non-plated hole
Effective surface soldering area
Minimum good ring width
Figure 4 The design width of the solder mask or double cover clearance window in the permanent protective coating shall be equal to the width of the minimum effective soldering area plus the process tolerance. When agreed by the manufacturer, the process tolerance is equal to the minimum tolerance PT1.
In many cases, the size of the double-coated opening depends on how much of the conductor closest to the pad needs to be covered. When the coating of such a conductor has specific requirements, the design width of the corresponding solder mask or double cover layer area should be equal to the width of the coated area plus the process tolerance, which is equal to the minimum tolerance PT2 if agreed by the printed board manufacturer. When only approximate values are required, PT1 and PT2 can be considered equal. Solder Mask Tolerance
The solder mask tolerance of epoxy glass cloth boards that have not been solder fused can refer to the following guidelines. For photo-imaging processes, the position tolerance can be 0.1mm to 0.6mm depending on the size of the product being imaged and the positioning method. For screen printing processes, the position tolerance can be 0.4mm to 1.0mm. Cover Layer Tolerance
For processes where the double cover layer is punched or drilled and then laminated, the process tolerance can be 0.5mm to 1.5mm. Appendix A lists an example of solder mask or cover layer. 3.3.4 Conformal Coatings
3.3.4.1 Overview
Conformal coatings are electrically insulating materials applied to printed boards or printed board assemblies to act as a protective barrier to the environment.2 Permanent solder resist
This coating is applied before the soldering operation to cover the specified area of the printed board to prevent the conductive pattern in the area from being wetted by solder. It is different from the temporary solder resist of the stripping type or washing type. After the soldering operation, the permanent solder resist cannot be removed, but acts as a permanent protective coating. When used only as a solder resist, it should have sufficient protective properties in addition to other necessary properties. Solder resist as a permanent protective coating can also be applied to the component side, in which case it only acts as a permanent protective coating.
Solder resist can be used for one or more of the following reasons: a) Prevent the specified area from being wetted by solder;
b) Prevent bridging between adjacent conductive patterns; c) Concentrate solder on the conductive pattern portion not covered by the solder resist, promote and improve solderability; d) Reduce solder consumption and solder tank contamination; e) Protect the printed board during processing;
() Improve or maintain the electrical performance of the printed board: g) Act as an insulating layer between the component body and the conductive pattern below it. If the material of the conductive pattern, such as solder, is easily molten during the soldering process, the solder resist applied over it may wrinkle, blister, or peel after soldering.
Selectively avoiding the application of solder resist over the solder or, for example, applying a thicker solder resist layer over the solder (which also acts as a thermal barrier), using thinner solder layers, designing thin wires, and opening windows in large conductive patterns can reduce wrinkling, blistering, or peeling. If wrinkling, blistering, or peeling is unacceptable, a solution should be proposed for change. There are two basic types of solder resists commonly used: printed types, generally screen printing, which is to print the solder resist on the specified printed board pattern; photoimageable solder resist, which is to apply a special wet or dry film on the printed board, and then produce the corresponding pattern after exposure (usually ultraviolet light) and development
Screen printing is usually less expensive, but using photoimageable solder resist can achieve tighter tolerances (see 3.3.3.4). Misalignment between the solder mask clearance window and the land, as well as diameter deviations between the land and solder mask clearance window, may cause the land to be partially covered, reducing the soldering area. When necessary, the relevant specifications should specify appropriate size and overlap requirements. 3.3.3.3 Covering layer
The covering layer is an insulating protective layer covering the surface of the printed board. It is usually a film or insulating metal foil bonded to the surface of the flexible printed board with an adhesive. It can also be made on a rigid printed board by processes such as pre-molding materials and lamination. In addition to the clearance window for welding and contact, the covering layer covers the entire surface of the printed board. The cover layer of the flexible printed board covers the surface conductor to improve or maintain the electrical performance and flexibility of the printed board. The covering layer is usually 0.025 mm thick plus the thickness of the adhesive, and its size is unstable. It must be considered when determining the minimum ring width with sufficient pad area.
To protect the unsupported hole lands on flexible printed boards from lifting from the substrate surface, a toe can be added to such lands or a cover layer can be used to cover the land circumference, see Figure 2. 0.25mn
Residual window of cover layer
d—drilling hole diameter: D—
-Residual window diameter:
Minimum distance: y-
Figure 2 Methods for strengthening pads
Engagement width of short-term cover layer.
It is not practical to use a single cover layer clearance window in a dense solder joint area (such as a connector structure), so this window can be made into the structure shown in Figure 3. For unsupported holes, a toe should be added to the copper land. It is not appropriate to use a cover layer on a flexible printed board to cover the metal coating area that is easily melted during the soldering operation. The cover layer may wrinkle and/or blister after the soldering operation. Combined method
Preferred
Acceptable
Strip window method
Figure 3 Preferred window shape
Single window method
Excerpt
Acceptable
GB/T4588.3—2002
1. The combined method and the single window method are the most expensive. The strip window method is prone to a weak point, that is, the copper and the substrate may crack here. 2. The single window method is used for flexible printed boards with low-density connection pads. 3. The strip window method or combined method is used for flexible printed boards with high-density connection pads. 4. The strip window method (bare wire) always requires additional coating of a certain coating or potting compound to provide more adhesion support for the bare wire after the part is assembled to the conductive pattern.
5. The combined method (bare wire) always requires additional coating of a certain coating or potting compound to provide more adhesion support for the bare wire after the part is assembled to the conductive pattern.
3.3.3.4 Tolerances and Design of Solder Mask Pattern or Covering The product design and final product requirements shall include process tolerances for the position and size of the solder mask or cover clearance window. A certain area (including size and position) not covered by the solder mask or cover is usually specified as the minimum effective soldering area (see Figure 4). When this area includes component soldering holes, the minimum value of the solderable ring width may replace the position and size tolerances with the agreement of both the supplier and the buyer.
Width of effective solder pad
Permanent protective coating
Thickness hole or non-plated hole
Effective surface soldering area
Minimum good ring width
Figure 4 The design width of the solder mask or double cover clearance window in the permanent protective coating shall be equal to the width of the minimum effective soldering area plus the process tolerance. When agreed by the manufacturer, the process tolerance is equal to the minimum tolerance PT1.
In many cases, the size of the double-coated opening depends on how much of the conductor closest to the pad needs to be covered. When the coating of such a conductor has specific requirements, the design width of the corresponding solder mask or double cover layer area should be equal to the width of the coated area plus the process tolerance, which is equal to the minimum tolerance PT2 if agreed by the printed board manufacturer. When only approximate values are required, PT1 and PT2 can be considered equal. Solder Mask Tolerance
The solder mask tolerance of epoxy glass cloth boards that have not been solder fused can refer to the following guidelines. For photo-imaging processes, the position tolerance can be 0.1mm to 0.6mm depending on the size of the product being imaged and the positioning method. For screen printing processes, the position tolerance can be 0.4mm to 1.0mm. Cover Layer Tolerance
For processes where the double cover layer is punched or drilled and then laminated, the process tolerance can be 0.5mm to 1.5mm. Appendix A lists an example of solder mask or cover layer. 3.3.4 Conformal Coatings
3.3.4.1 Overview
Conformal coatings are electrically insulating materials applied to printed boards or printed board assemblies to act as a protective barrier to the environment.0.25mm plus the thickness of the adhesive, and its size is unstable. It must be considered when determining the minimum ring width with sufficient pad area.
In order to protect the unsupported hole connection land on the flexible printed board from lifting from the substrate surface, a toe can be added to the connection land or a cover layer can be used to cover the circumference of the connection land, see Figure 2. 0.25mn
Residual window of the cover layer
d—drilling hole diameter: D—
—Residual window diameter:
Minimum distance: y-
Figure 2 Methods for strengthening the pad
Engagement width of the short benefit layer.
It is not practical to use a single cover layer clearance window in a dense solder joint area (such as a connector structure), so this window can be made into the structure shown in Figure 3. For unsupported holes, a toe should be added to the copper connection land. It is not appropriate to use a cover layer on a flexible printed board to cover the metal coating area that is easily melted during the soldering operation. The cover may wrinkle and/or blister after the soldering operation. Combined method
Preferred
Acceptable
Strip window method
Figure 3 Window shape
Single window method
Excerpt
Acceptable
GB/T4588.3—2002
1. Combined method and single window method are the most expensive. The strip window method is prone to a weak point, that is, the copper and substrate may crack here. 2. The single window method is used for flexible printed boards with low density of connection pads. 3. The strip self-opening or combined method is used for flexible printed boards with high density of connection pads. 4. The strip window method (bare wire) always requires additional coating or encapsulation compound to provide more adhesion support for the bare wire after the part is assembled to the conductive pattern.
5. The joint method (bare wire) always requires additional coating or potting compound to provide more adhesion support for the wire after the part is assembled on the conductive pattern.
3.3.3.4 Tolerance and design of solder mask pattern or cover layer Product design and final product requirements should include process tolerances in position and size of the solder mask or cover layer clearance window. Usually, an area not covered by solder mask or cover layer (including size and position) is specified as the minimum effective soldering area (see Figure 4). When this area contains component solder holes, the minimum value of the solderable ring width can replace the position and size tolerances with the agreement of both the supplier and the buyer.
Effective pad width
Permanent protective coating
High-pass hole or non-plated hole
Effective surface soldering area
Minimum acceptable ring width
Figure 4. The design width of the window for solder mask or double cover clearance in permanent protective coating should be equal to the width of the minimum effective soldering area plus the process tolerance, which is equal to the minimum tolerance PT1 when agreed by the manufacturer.
In many cases, the size of the double-coated opening depends on how much of the conductor closest to the pad needs to be covered. When there are specific requirements for the coating of such conductors, the design width of the corresponding solder mask or double cover area should be equal to the width of the coating area plus the process tolerance, which is equal to the minimum tolerance PT2 when agreed by the printed board manufacturer. When only approximate values are required, PT1 and PT2 can be regarded as equal. Solder mask tolerance
The solder mask tolerance of epoxy glass cloth boards that have not been fused with solder can be found in the following guidelines. For photo-imaging processes, the position tolerance can be 0.1mm to 0.6mm, depending on the size of the product being imaged and the positioning method. For screen printing processes, the position tolerance can be 0.4mm to 1.0mm. Cover layer tolerance
For processes where the double cover layer is punched or drilled before lamination, the process tolerance can be 0.5mm to 1.5mm. Appendix A gives an example of a solder mask or cover layer. 3.3.4 Conformal coating
3.3.4.1 Overview
Conformal coating is an electrically insulating material applied to a printed board or printed board assembly as a protective barrier to block the 90.25mm plus the thickness of the adhesive, and its size is unstable. It must be considered when determining the minimum ring width with sufficient pad area.
In order to protect the unsupported hole connection land on the flexible printed board from lifting from the substrate surface, a toe can be added to the connection land or a cover layer can be used to cover the circumference of the connection land, see Figure 2. 0.25mn
Residual window of the cover layer
d—drilling hole diameter: D—
—Residual window diameter:
Minimum distance: y-
Figure 2 Methods for strengthening the pad
Engagement width of the short benefit layer.
It is not practical to use a single cover layer clearance window in a dense solder joint area (such as a connector structure), so this window can be made into the structure shown in Figure 3. For unsupported holes, a toe should be added to the copper connection land. It is not appropriate to use a cover layer on a flexible printed board to cover the metal coating area that is easily melted during the soldering operation. The cover may wrinkle and/or blister after the soldering operation. Combined method
Preferred
Acceptable
Strip window method
Figure 3 Window shape
Single window method
Excerpt
Acceptable
GB/T4588.3—2002
1. Combined method and single window method are the most expensive. The strip window method is prone to a weak point, that is, the copper and substrate may crack here. 2. The single window method is used for flexible printed boards with low density of connection pads. 3. The strip self-opening or combined method is used for flexible printed boards with high density of connection pads. 4. The strip window method (bare wire) always requires additional coating or encapsulation compound to provide more adhesion support for the bare wire after the part is assembled to the conductive pattern.
5. The joint method (bare wire) always requires additional coating or potting compound to provide more adhesion support for the wire after the part is assembled on the conductive pattern.
3.3.3.4 Tolerance and design of solder mask pattern or cover layer Product design and final product requirements should include process tolerances in position and size of the solder mask or cover layer clearance window. Usually, an area not covered by solder mask or cover layer (including size and position) is specified as the minimum effective soldering area (see Figure 4). When this area contains component solder holes, the minimum value of the solderable ring width can replace the position and size tolerances with the agreement of both the supplier and the buyer.
Effective pad width
Permanent protective coating
High-pass hole or non-plated hole
Effective surface soldering area
Minimum acceptable ring width
Figure 4. The design width of the window for solder mask or double cover clearance in permanent protective coating should be equal to the width of the minimum effective soldering area plus the process tolerance, which is equal to the minimum tolerance PT1 when agreed by the manufacturer.
In many cases, the size of the double-coated opening depends on how much of the conductor closest to the pad needs to be covered. When there are specific requirements for the coating of such conductors, the design width of the corresponding solder mask or double cover area should be equal to the width of the coating area plus the process tolerance, which is equal to the minimum tolerance PT2 when agreed by the printed board manufacturer. When only approximate values are required, PT1 and PT2 can be regarded as equal. Solder mask tolerance
The solder mask tolerance of epoxy glass cloth boards that have not been fused with solder can be found in the following guidelines. For photo-imaging processes, the position tolerance can be 0.1mm to 0.6mm, depending on the size of the product being imaged and the positioning method. For screen printing processes, the position tolerance can be 0.4mm to 1.0mm. Cover layer tolerance
For processes where the double cover layer is punched or drilled before lamination, the process tolerance can be 0.5mm to 1.5mm. Appendix A gives an example of a solder mask or cover layer. 3.3.4 Conformal coating
3.3.4.1 Overview
Conformal coating is an electrically insulating material applied to a printed board or printed board assembly as a protective barrier to block the 9
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