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1、BRITISH STANDARD BS 6221-22: 1990 Printed wiring boards Part 22: Guide to the use of printed wiring board substrate materials: surface mount technology Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 07:55:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6221-22:1990 This British Standard, ha
2、ving been prepared under the direction of the Electronic Components Standards Policy Committee, was published under the authority of the Board of BSI and comes into effect on 31 December 1990 BSI 04-1999 The following BSI references relate to the work on this standard: Committee reference ECL/19 Dra
3、ft for comment 88/31464 DC ISBN 0 580 18031 X Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Electronic Components Standards Policy Committee (ECL/-) to Technical Committee ECL/19, upon which the following bodies were represented: Briti
4、sh Telecommunications plc ERA Technology Ltd. Electrical and Electronic Insulation Association (BEAMA Ltd.) Electronic Components Industry Federation GAMBICA (BEAMA Ltd.) Institute of Circuit Technology Institute of Metal Finishing Institution of Production Engineers Ministry of Defence National Sup
5、ervising Inspectorate Printed Circuit Association Telecommunications Engineering and Manufacturing Association (TEMA) Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 07:55:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6221-22:1990 BS
6、I 04-1999i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2General1 3Introduction to base laminate materials1 4Material specifications3 5Phenolic resin based copper-clad laminates3 6Epoxide resin based copper-clad laminates3 7Polyimide resin based copper-clad laminates4 8P
7、olyester resin based copper-clad laminates4 9Silicone resin based copper-clad laminates5 10Polytetrafluoroethylene (PTFE) resin based copper-clad laminates5 11Compliant layer copper-clad laminates5 12Metallurgically bonded laminates5 13Ceramic base materials6 14Typical comparative material propertie
8、s7 Figure 1 Examples of a four multilayer board lay-up7 Figure 2 Example of a six layer multilayer board lay-up7 Table 1 Comparative properties of phenolic resin and epoxide resin based materials8 Table 2 Comparative properties of polyimide resin and polyester resin based materials9 Table 3 Comparat
9、ive properties of silicone resin and PTFE resin based materials10 Table 4 Comparative properties of alumina, copper-clad invar, copper-clad molybdenum and compliant layer materials11 Publications referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 07:55:27 GMT+00:00 2
10、006, Uncontrolled Copy, (c) BSI BS 6221-22:1990 ii BSI 04-1999 Foreword This British Standard has been prepared under the direction of the Electronic Components Standards Policy Committee. This Part of BS 6221 provides guidance on the manufacture and properties of printed wiring board base laminate
11、materials with particular reference to their use in surface mount technology and should therefore be used in conjunction with BS 6221-3, BS 6221-4, BS 6221-5, BS 6221-6, BS 6221-7, BS 6221-8, BS 6221-20 and BS 6221-21. A British Standard does not purport to include all the necessary provisions of a
12、contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 12, an inside ba
13、ck cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 07:55:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI
14、 BS 6221-22:1990 BSI 04-19991 1 Scope This Part of BS 6221 provides guidance on the manufacture and properties of printed wiring board base laminate materials. Particular emphasis is given to their use in surface mount technology (SMT). While the major types of resin systems are covered, together wi
15、th the appropriate reinforcements, this guide is not exhaustive. For definitive properties of the resin/reinforcement systems described, and of other available systems, the laminate manufacturers should be consulted. 2 General 2.1 The material for printed wiring boards will usually be metal-clad syn
16、thetic resin bonded sheet or metal-clad polymeric film where the conductor pattern is chemically etched or mechanically milled, or unclad synthetic resin bonded sheet or polymeric film where the conductor pattern is formed by additive methods such as plating, die stamping or by discrete wiring techn
17、iques. 2.2 The material selected should have a specification which is properly matched to the performance required. The aim should be to achieve reliability at minimum cost. 2.3 Where properties of particular materials are quoted in this document they are intended only for guidance. When considering
18、 specific applications the material specifications should be consulted in conjunction with the material manufacturer. 2.4 Although most substrate materials can be used for the surface mounting of components there are certain copper-clad laminates and combinations of copper-clad laminates which are m
19、ost suited to this application. Such materials and combinations of materials assist in minimizing the thermal coefficient of expansion (TCE) differences between the substrate materials and the components. 3 Introduction to base laminate materials 3.1 General A printed wiring board (PWB) substrate la
20、minate is composed of an insulating material with copper foil bonded to one or both sides. The insulating material is normally a composite comprising a resin matrix and a reinforcing filler. 3.2 Insulating material 3.2.1 Resin types in usage include the following: a) phenolic; b) epoxide; c) polyimi
21、de; d) silicone; e) PTFE. 3.2.2 Resins have differing characteristic properties which determine their suitability for particular applications. Taking just two examples the characteristics of phenolic and epoxide resins differ as follows. a) Phenolic. Low cost. Workhorse for non-critical consumer PWB
22、 market. Reduced mechanical and electrical properties (compared with epoxide). High moisture uptake. b) Epoxide. Medium cost. Workhorse for professional PWB market. Excellent processability. Reasonable performance in all mechanical and electrical properties. 3.2.3 Resins used for PWB laminate manufa
23、cture fall into two categories. a) Thermoplastic. These can be repeatedly softened and moulded by heat and pressure. b) Thermosetting. These can be cured and set by the action of heat to form a cross linked relatively infusible structure. 3.2.4 The most widely used PWB laminate resin type is epoxide
24、, which is thermosetting and as such once formed is permanently set in position and cannot be remelted on heating. Cured epoxide resins are produced in two stages: a) production of incompletely reacted prepolymer, which is accomplished during resin blending and impregnation; b) conversion to final c
25、ross linked product, which is accomplished during lamination. 3.2.5 Reinforcements (fillers) are mainly comprised of glass fibre or paper. Some examples are: a) glass fibre which may be woven or random (non-woven); b) paper; c) aramid; d) composite (such as paper plus woven glass or random (non-wove
26、n) plus woven glass). 3.2.6 The most widely used reinforcement is woven glass. The particular grade normally chosen is designated “E” (for electrical) glass. The properties required of the woven glass include the following: a) good electrical properties; b) good dimensional stability; c) good chemic
27、al resistance; d) low water absorption; e) high tensile strength; f) good heat resistance. Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 07:55:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6221-22:1990 2 BSI 04-1999 3.2.7 The glass is formed from a melt into filaments of between 4 m and
28、12 m which are then gathered into strands of up to 1 600 filaments. These strands are then woven into a fabric. The woven fabric has an organic coating, known as a finish, applied to its surface to aid the subsequent bond to the resin used. 3.2.8 The decision as to which particular resin/filler comb
29、ination is selected depends on the application. Some considerations are as follows. a) Electrical properties: dielectric constant, dissipation factor, volumetric and surface resistance, dielectric strength. b) Mechanical properties: tensile, compressive, shear, flexural and impact strength, dimensio
30、nal stability, processability, glass transition temperature, coefficient of thermal expansion. c) Environmental properties: water absorption, copper migration resistance, operating temperature, flammability. 3.3 Copper foil Copper foil is produced mainly by electrolytic deposition giving a typical m
31、inimum purity of 99.5 %. The method of production involves electroplating from an electrolyte containing a copper salt onto a revolving highly polished stainless steel or titanium drum. The side facing away from the drum (matt side) is further processed in order to increase its surface area which wi
32、ll then ultimately impart a high peel strength to the final laminate. Properties required from copper foil include the following: a) low electrical resistance; b) freedom from pinholes, scratches, holes and nodules; c) controlled ductility; d) controlled thickness; e) good solderability. 3.4 Laminat
33、e production 3.4.1 Stages PWB laminates are normally produced in three discrete stages: a) impregnation of reinforcement; b) lay-up of prepregs; c) lamination. 3.4.2 Impregnation During the impregnation stage the reinforcement is coated with a blend of resin dissolved in a solvent or a solvent mixtu
34、re. The reinforcement is drawn through a trough containing the resin blend and then through a multi-zone oven where the solvents are evaporated and the resin is allowed to partially react leaving a coating of dry resin advanced to a controlled degree of cure. Woven glass materials are normally impre
35、gnated in vertical machines, whereas paper and non-woven fabrics are normally impregnated in horizontal machines. The material produced by the impregnator is known as “prepreg” (for pre-impregnated) or “B” stage. 3.4.3 Lay-up of prepregs The prepreg is assembled into the correct number of pieces for
36、 the required laminate thickness. In the case of 1.6 mm epoxide resin/woven glass this would normally be eight plies. The assembly is then faced with copper foil and each individual laminate (copper foil/prepreg/copper foil) is separated with polished stainless steel plates to impart a high quality
37、surface finish. Laminates are produced as above in stacks suitable for loading into a multi-opening laminating press. 3.4.4 Lamination Laid up laminate stacks are loaded into multi-opening laminating presses where they are subjected to a hydraulic pressure and temperature cycle for the period of tim
38、e necessary to achieve a satisfactory level of curing reaction. Following this they are cooled and trimmed to the required size awaiting inspection and testing. 3.5 Inspection and testing Parameters measured on finished laminates include the following. a) Electrical: resistance of foil, surface resi
39、stance, volume resisitivity, surface corrosion, corrosion at the edge, comparative tracking index, permittivity (dielectric constant), dissipation factor, electric strength, resistance to copper migration. b) Non-electrical: bow, twist, pull-off strength of lands, peel strength of conductors, bliste
40、ring after heat shock, punching and machining, surface finish, solderability, dimensional stability, flexural fatigue, flexural strength, mass of foil, thickness, flammability, water absorption. Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 07:55:27 GMT+00:00 2006, Uncontrolled Copy, (c) BS
41、I BS 6221-22:1990 BSI 04-19993 4 Material specifications 4.1 Reference should be made to the specifications for metal-clad base materials for printed wiring boards given in BS 4584. 4.2 If there is not a suitable material specification given in the BS 4584 series of specifications a suitable specifi
42、cation detailing its properties should be drafted: a) in conjunction with a material supplier; b) using the methods of test given in BS 4584-1:1983; c) following the layout and format of BS 4584 specifications. 4.3 Where special properties are essential, they should be defined and specified in colla
43、boration with a material supplier. 5 Phenolic resin based copper-clad laminates 5.1 Phenolic resin based copper-clad laminates are normally manufactured from resin impregnated cellulose paper bonded together in sheets to form the base material. The material is manufactured in different qualities, fr
44、om economic grade to high electrical grade with various flame retardant properties. 5.2 Maximum operating temperatures of the various grades range from 70 C to 100 C. However, long term operation at temperatures towards the higher end of the range may cause degradation of certain properties. Excessi
45、ve heating can result in carbonization and in the areas affected the insulation resistance (bulk and surface) may fall to a very low level. When operating within the normal temperature range a severe darkening can occur due to natural ageing, e.g. ageing due to the effects of sunlight. In these inst
46、ances no significant loss of properties is involved. 5.3 Exposure to high humidity can significantly reduce the insulation resistance of this material although the condition will naturally recover when the humidity falls to a lower level. 5.4 When using this material for the surface mounting of comp
47、onents consideration should be given to its limitations in terms of printed wiring board processing and component assembly processing. Its dimensional stability may not be suitable for high density component interconnection. The materials are not suitable for the mounting of high pin count (28 or mo
48、re) ceramic components and the time/temperature profiles of some surface mount assembly processes may affect the materials electrical and mechanical properties. 5.5 The material can be punched as well as drilled and is relatively cheap. 5.6 The specifications covering this material are BS 4584-102.1
49、, BS 4584-102.2, BS 4584-102.6, BS 4584-102.7 and BS 4584-102.14. 6 Epoxide resin based copper-clad laminates 6.1 General 6.1.1 Epoxide resin based laminates are normally laminated from resin impregnated “E” glass or cellulose paper or both. The glass reinforcement can either be in the form of a woven fabric or a random mat. Typical structures are: a) epoxide resin, cellulose paper copper-clad laminated sheet; b) epoxide resin, paper core, epoxide woven glass outer layers copper-clad laminated sheet; c) epoxide resin, woven/non-woven glass copper- clad laminated