1、BRITISH STANDARD Printed boards and assemblies - Design and use Part 1. Generic requirements Section 1. Flatness considerations for electronic assemblies * * rJ3 The European Standard EN 611881-1 : 1997 has the status of a British Standard Ics31.180 BS EN 61188-1-1 : 1997 IEC 61188-1-1 : 1997 NO COP
2、YING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW *WrnWWW STD.BS1 BS EN bLL-1-L-ENGL 1777 II lb24bb Ohb7958 20T W Amd. No. - BS EN 61188-1-1 : 1997 Date Text affected National foreword This British Standard is the English ianguage version of EN 61188-1-1. : 1997. It is identical with
3、IEC 611881-1 : 1997. The UK participation in its preparation was entrusted to Technical Committee EPUSO1, Electronic assembly technology, which has the responsibility to: - aid enquirers to understand the text; - present to the responsible internationailEuropean committee any enqukic ?3 on the inter
4、pretation, or proposals for change, and keep the UK interests informed - monitor related international and European developments and prornugatt. them in the UK. A list of organizations represented on this committee can be obtained on requcsl tri its secretary. From 1 January 1997, all IEC publicatio
5、ns have the number 60000 adceed to the old number. For instance, IEC 27-1 has been renumbered as IEC 60027-1. 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 Attention is drawn to the fact th
6、at CEN and CENELEC Standards iionnally include an annex which lists normative references to international publications with their corresponding European publications. The British Standards which implement th(w international or European publications may be found in the BSI Star idards Catalogue under
7、 the section entitled ?International Standards Correspondence Index?, or by using the ?Find facility of the BSI Standards Electronic Catalogue. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an ins
8、ide front cover, the EN title page, pages 2 to 13, a blank page, an Mide back cover and a back cover. This British Standard, having been prepared under the diredon of the Electrotechnical Sector Board, was published under the authonS. of the Standards Board and comes into effect on 15 December 1997
9、BSI 1997 :80 28734 3 EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 61 188-1-1 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 asse
10、mblies - Design and use Part 1-1 : Generic requirements - Flatness considerations for electronic assemblies (IEC 61 188-1-1 11 997) Cartes imprimes et cartes imprimes quipes - Conception et utilisation Partie 1-1 : Prescriptions gnriques Considrations concernant ia planit densembles lectroniques ele
11、ktronischen Baugruppen Le te rplatten und Fi a c h b augru p pen Konstruktion und Anwendung Teil 1-1 : Allgemeine Anforderungen Gesichtspunkte zur Ebenheit von (CE1 61 188-1-1:1997) (IEC 61 188-1-1:1997) This European Standard was approved by CENELEC on 1997-1 0-01. CENELEC members are bound to comp
12、ly with the CENKENELEC Internal 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 Secr
13、etariat or to any CENELEC 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
14、the official versions. CENELEC 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 Electr
15、otechnical Standardization 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. N
16、o. EN 61188-1-1:1997 E Page 2 EN 61188-1-1 : 1997 Foreword The text of document 52/721/FDIS, future edition 1 of IEC 61 188-1-1, prepared by IEC TC 52, Printed circuits, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 61 188-1-1 on 1997-10-01. The following dates wer
17、e fixed: - 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 by which the national standards conflicting with the EN have to be withdrawn (daw) 1 998-07-0 1 Annexes designated “normati
18、ve“ 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 IEC 61 188-1 -1 : 1997 was approved by CENELEC as a European Standard without any modification. STD-BSI BS EN bLLBB-1-1-ENG
19、L 1997 Lb24bb9 Obb79bl AT4 111 . = E * * rn Page 3 EN 61188-1-1 : 1997 CONTENTS Page INTRODUCTION . 4 Clause scope . Normative reference . Basic requirements . 3.1 Design 3.2 Rigid board manufacture 3.3 Assembly 3.4 Use Deviations from flatness - Rigid copper-clad base material 4.1 Causes . 4.2 Prev
20、ention and correction 4.3 Test methods and requirements Deviations from flatness - Unassembied rigid printed boards . 5.1 Causes . 5.2 Prevention 5.3 Rectification 5.4 Requirements for flatness 5.5 Measurement methods Deviations from flatness - Rigid printed board assemblies . 6.1 Causes . 6.2 Preve
21、ntion 6.3 Correction . Problems associated .with placement of surface-mounted components 7.1 Placement of components (assembly) . 7.2 Requirements for pick-and-place“ machines Deviations from flatness in service . Prevention summafy 5 5 5 5 5 6 6 6 6 7 7 7 7 9 9 9 10 10 10 11 11 11 11 11 12 12 10 Co
22、rrective action summaty . 12 Annex ZA (normative) Normative references to international publications with their corresponding European publications 13 O BSI 1997 STD-BSI BS EN bLL8-1-1-ENGL 1997 m Lb24bb9 Obb77b2 730 U Page 4 EN 61188-1-1 : 1997 INTRODUCTION Rigid printed board technology demands a
23、high degree of flatness in substrates and assemblies and distortion may result from a number of causes. All individuals involved 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 unde
24、r their control. The following table shows the references to the three test methods given in IEC 61 189-2. Bow and twist test method checklist for materials I Parameter I Condition I EC61189-2 Test No. I As received After processing Twist As received 2M01 Twist After processing 2M04 Page 5 EN 61188-
25、1-1 : 1997 PRINTED BOARDS AND PRINTED BOARD ASSEMBLIES - DESIGN AND USE - Part 1-1 : Generic requirements - Flatness considerations for electronic assemblies 1 Scope This part of IEC 61188 describes those factors which control the flatness of rigid printed boards and their assemblies. The object of
26、this standard is to inform the designer; manufacturer, assembler and user of rigid printed boards and their assemblies about those factors affecting their flatness. This standard incorporates advice regarding: - design (clause 3); - base material (clause 4); - unassembled printed boards (clause 5);
27、- printed board assemblies (clause 6). 2 Normative reference The following normative documents contain provisions which, through reference in this text, constitute provisions of this part of IEC 61 188. At the time of publication, the editions indicated were valid. All normative documents are subjec
28、t to revision, and parties to agreements based on this part of IEC 61188 are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. Members of IEC and IS0 maintain registers of currently valid International Standards. IEC 61 189-2:
29、1977, Test methods for electrical materials, interconnection structures and assemblies - Part 2: Test methods for materials for interconnection structures 3 Basic requirements 3.1 Design The designer of the rigid board/assembly shall aim to achieve a mechanically balanced construction. For the print
30、ed board, balanced construction pertains to the even distribution of the amount of resin, reinforcement and metallic foil about the centre of the board in any axis. in addition, if metal is bonded to the substrate (e.9. as a heat sink) the contribution to flatness provided by the metal must be under
31、stood. Printed board assemblies usually have components on only one side. However, with the advent of surface mounting, many designs have both sides 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
32、the flatness characteristics of the assembly. 3.2 Rigid board manufacture The rigid board manufacturer shall consider how to use and process the material to minimize distortion. Page 6 EN 61188-1-1 : 1997 3.3 Assembly The rigid board assembler shall try to ensure that no distortion is introduced, pa
33、rticularly during soldering and handling operations. 3.4 Use The user shall, by good storage and equipment practice, minimize the likelihood of distortion occurring after assembly. 4 Deviations from flatness - Rigid copper-clad base material 4.1 Causes The following can contribute, either singly or
34、in combination, to distortion of copper-clad material. 4.1 .l Reinforcement Glass fabrics may be stressed during weaving and treatment. Distortion of the laminated product introduced by individual sheets of stressed glass fabric will be small. 4.1.2 Copper foil The effect of the copper foil on disto
35、rtion is usually small. 4.1.3 6-stage material (prepreg) Impregnation of the reinforcement with resin, which is subsequently partially cured, produces “B-stage“ base material (prepreg). Non-uniform impregnation can produce stresses which result in distortion in the laminated product. These stresses
36、may be attributed to: - uneven tension applied to the reinforcement as it passes through the treater (resin i m p regnator) ; - 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.
37、4.1.4 Lamination Non-uniform laminating pressure and temperature builds in stresses. Unbalanced construction, .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
38、 greater will be 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. STD.BS1 B
39、S EN bllAA-1-1-ENGL 1997 D Lb24bb7 Obb77b5 44T Page 7 EN 61188-1-1 : 1997 4.2 Prevention and correction To minimize distortion the factors discussed in 4.1 shall be controlled. Attention will be paid to the design engineering and specification. Process control has to be performed. Once lamination ha
40、s been completed corrective action is not possible if internal stresses have been built into the base material. Glass transition temperature (i ): The Tg is the temperature at which a thermosetting plastic changes from a glass-like (ri the material will behave like a glass below the Tg and like defo
41、rmable material above it. Therefore, deformations introduced in the deformable state will be locked in when the material reverts to the glass-like state. The Tg of epoxide woven glass fabric materiais in common use is normally in the range of 120 OC to 135 OC but can be as low as 105 OC. Other resin
42、s can have a significantly different Tg. If the laminated material is not flat at room temperature, the presence of internai 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 Tg of the resin, th
43、e resin no longer restrains 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 l
44、g but may reappear on reheating. 4.3 Test methods and requirements Test methods and values for a range of commonly used base materials are given in IEC 61 189-2. Where there is no existing specification for the material being used in the IEC or equivalent national standards, it is recommended that a
45、greement be reached between customer and supplier on limit values to be obtained using the accepted international standard test method. - II = _. - - = * * 5 Deviations from flatness - Unassembled rigid printed boards m 5.1 Causes The following can contribute, either singly or in combination, to dis
46、tortion of unassembled rigid printed boards. 5.1.1 Printed board design 5.1 .l. 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.
47、Designs incorporating rigid printed board profiles blanked and returned to panel may aggravate distortion. Page 8 EN 61188-1-1 : 1997 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 t
48、hickness of copper in the design, the greater will be the distortion. Twist is 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 asymmetr
49、ical lay-up about the centre plane of the board will produce permanent distortion. Examples are disposing power and/or ground planes on one side of the centre plane, say as layers 4 and 5 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 fac
