1、BRITISH STANDARD BS EN 61188-1-1:1997 IEC61188-1-1: 1997 Printed boards and assemblies Design and use Part 1: Generic requirements Section 1: Flatness considerations for electronic assemblies The European Standard EN 61188-1-1:1997 has the status of a British Standard ICS 31.180BSEN 61188-1-1:1997 T
2、his British Standard, having been prepared under the directionof the Electrotechnical Sector Board, was published underthe authority of the Standards Board and comes into effect on 15December1997 BSI 03-1999 ISBN 0 580 28734 3 National foreword This British Standard is the English language version o
3、f EN61188-1-1:1997. It is identical with IEC61188-1-1:1997. The UK participation in its preparation was entrusted to Technical Committee EPL/501, Electronic assembly technology, which has the responsibility to: aid enquirers to understand the text; present to the responsible international/European c
4、ommittee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this committee can be obtained on request to its secretary. From 1
5、January 1997, all IEC publications have the number60000 added to the old number. For instance, IEC27-1 has been renumbered as IEC60027-1. For a period of time during the change over from one numbering system to the other, publications may contain identifiers from both systems. Cross-references Atten
6、tion is drawn to the fact that CEN and CENELEC Standards normally include an annex which lists normative references to international publications with their corresponding European publications. The British Standards which implement these international or European publications may be found in the BSI
7、 Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are respons
8、ible 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, theEN title page, pages 2 to 8 and a back cover. This standard has been upd
9、ated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No. Date CommentsBSEN61188-1-1:1997 BSI 03-1999 i Contents Page National foreword Inside front cover Foreword 2 Text o
10、f EN 61188-1-1 3ii blankEUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 61188-1-1 October 1997 ICS 31.180 Descriptors: Printed circuits, printed boards and assemblies, design, use, basic requirements, deviations from flatness, placement of SMD English version Printed boards and printed board as
11、semblies Design and use Part1-1: Generic requirements Flatness considerations for electronic assemblies (IEC61188-1-1:1997) Cartes imprimes et cartes imprimes quipes Conception et utilisation Partie1-1: Prescriptions gnriques Considrations concernant la planit densembles lectroniques (CEI61188-1-1:1
12、997) Leiterplatten und Flachbaugruppen Konstruktion und Anwendung Teil1-1: Allgemeine Anforderungen Gesichtspunkte zur Ebenheit von elektronischen Baugruppen (IEC61188-1-1:1997) This European Standard was approved by CENELEC on 1997-10-01. CENELEC members are bound to comply with the CEN/CENELEC Int
13、ernal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC
14、member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions. CEN
15、ELEC members are the national electrotechnical committees of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CENELEC European Committee for Electrotechnical Standardization
16、 Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B-1050 Brussels 1997 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 61188-1-1:1997 EEN61188-
17、1-1:1997 BSI 03-1999 2 Foreword The text of document 52/721/FDIS, future edition1 of IEC61188-1-1, prepared by IEC TC52, Printed circuits, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN61188-1-1 on1997-10-01. The following dates were fixed: Annexes designated “norma
18、tive” are part of the body of the standard. In this standard,Annex ZA is normative. Annex ZA has been added by CENELEC. Endorsement notice The text of the International Standard IEC61188-1-1:1997 was approved by CENELEC as a European Standard without any modification. Contents Page Foreword 2 Introd
19、uction 3 1 Scope 3 2 Normative reference 3 3 Basic requirements 3 3.1 Design 3 3.2 Rigid board manufacture 3 3.3 Assembly 3 3.4 Use 3 4 Deviations from flatness Rigid copper-clad base material 3 4.1 Causes 3 4.2 Prevention and correction 4 4.3 Test methods and requirements 4 5 Deviations from flatne
20、ss Unassembled rigid printed boards 4 5.1 Causes 4 5.2 Prevention 5 5.3 Rectification 5 5.4 Requirements for flatness 6 5.5 Measurement methods 6 6 Deviations from flatness Rigid printed board assemblies 6 6.1 Causes 6 6.2 Prevention 6 6.3 Correction 6 7 Problems associated with placement of surface
21、-mounted components 7 7.1 Placement of components (assembly) 7 7.2 Requirements for “pick-and-place” machines 7 8 Deviations from flatness in service 7 9 Prevention summary 7 10 Corrective action summary 7 Annex ZA (normative) Normative references to international publications with their correspondi
22、ng European publications 8 Table 1 Manufacturing stages and preventive measures 7 Table 2 Manufacturing stages and corrective actions 7 latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 1998-07-01 latest date
23、by which the national standards conflicting with the EN have to be withdrawn (dow) 1998-07-01EN61188-1-1:1997 BSI 03-1999 3 Introduction Rigid printed board technology demands a high degree of flatness in substrates and assemblies and distortion may result from a number of causes. All individuals in
24、volved at any stage of design, manufacture and use shall be aware of and understand the potential problems. It is essential that they pay specific attention to those factors under their control. The following table shows the references to the three test methods given in IEC 61189-2. Bow and twist te
25、st method checklist for materials 1 Scope This part of IEC 61188 describes those factors which control the flatness of rigid printed boards and their assemblies. The object of this standard is to inform the designer, manufacturer, assembler and user of rigid printed boards and their assemblies about
26、 those factors affecting their flatness. This standard incorporates advice regarding: design (clause3); base material (clause4); unassembled printed boards (clause5); printed board assemblies (clause6). 2 Normative reference The following normative documents contain provisions which, through referen
27、ce in this text, constitute provisions of this part of IEC61188. At the time of publication, the editions indicated were valid. All normative documents are subject to revision, and parties to agreements based on this part of IEC61188 are encouraged to investigate the possibility of applying the most
28、 recent editions of the normative documents indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. IEC 61189-2:1977, Test methods for electrical materials, interconnection structures and assemblies Part2: Test methods for materials for interconnection
29、structures. 3 Basic requirements 3.1 Design The designer of the rigid board/assembly shall aim to achieve a mechanically balanced construction. For the printed board, balanced construction pertains to the even distribution of the amount of resin, reinforcement and metallic foil about the centre of t
30、he board in any axis. In addition, if metal is bonded to the substrate (e.g.as a heat sink) the contribution to flatness provided by the metal must be understood. Printed board assemblies usually have components on only one side. However, with the advent of surface mounting, many designs have both s
31、ides of the board populated with components. Proper location of components by size, weight and the number of leads to be attached to the board will improve the flatness characteristics of the assembly. 3.2 Rigid board manufacture The rigid board manufacturer shall consider how to use and process the
32、 material to minimize distortion. 3.3 Assembly The rigid board assembler shall try to ensure that no distortion is introduced, particularly during soldering and handling operations. 3.4 Use The user shall, by good storage and equipment practice, minimize the likelihood of distortion occurring after
33、assembly. 4 Deviations from flatness Rigid copper-clad base material 4.1 Causes The following can contribute, either singly or in combination, to distortion of copper-clad material. 4.1.1 Reinforcement Glass fabrics may be stressed during weaving and treatment. Distortion of the laminated product in
34、troduced by individual sheets of stressed glass fabric will be small. 4.1.2 Copper foil The effect of the copper foil on distortion is usually small. 4.1.3 B-stage material (prepreg) Impregnation of the reinforcement with resin, which is subsequently partially cured, produces “B-stage” base material
35、 (prepreg). Non-uniform impregnation can produce stresses which result in distortion in the laminated product. These stresses may be attributed to: uneven tension applied to the reinforcement as it passes through the treater (resin impregnator); Parameter Condition IEC 61189-2 Test No. Bow Bow Twist
36、 Twist As received After processing As received After processing 2M01 2M02 2M01 2M04EN61188-1-1:1997 4 BSI 03-1999 uneven or non-uniform thickness of resin across the reinforcement sheet width; improper curing (polymerization) of the resin, that is, under or over cure at the B-stage. 4.1.4 Laminatio
37、n Non-uniform laminating pressure and temperature builds in stresses. Unbalanced construction, i.e.plies which are out of alignment in the X and Y directions will cause stresses to be present. Foil on one side only of a laminate can make any distortion worse. The thicker the foil, the greater will b
38、e the distortion. In addition, when one side of a laminate is clad with thicker foil than the other, distortion can result. 4.1.5 Cutting and handling Cutting methods can induce stress. Storage of the finished material other than in the horizontal plane can cause distortion. 4.2 Prevention and corre
39、ction To minimize distortion the factors discussed in4.1 shall be controlled. Attention will be paid to the design engineering and specification. Process control has to be performed. Once lamination has been completed corrective action is not possible if internal stresses have been built into the ba
40、se material. Glass transition temperature (T g ): The T gis the temperature at which a thermosetting plastic changes from a glass-like (rigid) state to a deformable (flexible) state. This change is completely reversible; the material will behave like a glass below the T gand like deformable material
41、 above it. Therefore, deformations introduced in the deformable state will be locked in when the material reverts to the glass-like state. The T gof epoxide woven glass fabric materials in common use is normally in the range of120C to135C but can be as low as105C. Other resins can have a significant
42、ly different T g . If the laminated material is not flat at room temperature, the presence of internal stress is obvious. However, even if the material is flat at room temperature, internal stresses can still be present. When the material is heated above the T gof the resin, the resin no longer rest
43、rains the residual stresses and the material relaxes and appears flat. The distortion may, or may not, return if the base material is cooled down in an unrestrained condition. The distortion may be “corrected” by holding the base material flat while cooling to below the resin T gbut may reappear on
44、reheating. 4.3 Test methods and requirements Test methods and values for a range of commonly used base materials are given in IEC61189-2. Where there is no existing specification for the material being used in the IEC or equivalent national standards, it is recommended that agreement be reached betw
45、een customer and supplier on limit values to be obtained using the accepted international standard test method. 5 Deviations from flatness Unassembled rigid printed boards 5.1 Causes The following can contribute, either singly or in combination, to distortion of unassembled rigid printed boards. 5.1
46、.1 Printed board design 5.1.1.1 Rigid printed board profile The shape of the profile can influence the amount of distortion. 5.1.1.2 Internal cutouts Large cutouts with square corners or long slots centrally positioned may contribute to distortion. Designs incorporating rigid printed board profiles
47、blanked and returned to panel may aggravate distortion. 5.1.1.3 Density and layout of conductive patterns The distortion of single-sided rigid printed boards is most influenced by foil thickness. The greater the area and thickness of copper in the design, the greater will be the distortion. Twist is
48、 prevalent in designs containing uneven copper distribution; for example, a design which has a metallic plane on one side of the rigid board and pads on the other side. A rigid multilayer board design which has an asymmetrical lay-up about the centre plane of the board will produce permanent distort
49、ion. Examples are disposing power and/or ground planes on one side of the centre plane, say as layers4 and5 of a six-layer build, or using one thick thermal management layer rather than two thinner ones. 5.1.2 Rigid printed board processing 5.1.2.1 Shearing (guillotining) Shearing (guillotining) of panels from sheets of base material can induce stress at the very start of the manufacturing process (use of blunt blades, incorrect gap between the cutting faces, etc.).EN61188-1-1:1997 BSI 03-1999 5 5.1.2.2 Baki
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