美规UL标准SMT部件的固定

Liu

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美规产品要求焊接前要有机械固定，但是SMT部件是不可能穿过PCB焊接的，多次遇到厂家咨询此类问题，这里列出标准条款，供大家参考：
. m- b6 G: y* y6 q/ E: q$ oUL1993
* E% G/ w9 H5 _1 J1 V/ ?& k6.2.2 Where loosening or breaking of electrical connections involves a risk of fire or electric shock, the connections shall be soldered, welded, or otherwise securely connected. A soldered joint shall be mechanically secure before soldering. A surface mount component not exceeding a maximum dimension of 13 mm (0.5 in) need not comply with this requirement.
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UL8750
7.3.4 Soldered connections shall be mechanically secured before soldering.
Exception No. 4: Surface Mount Device (SMD) components and small components without integral leads do not need to be mechanically secured to the printed wiring board before soldering. Surface mounted connector receptacles and associated connectors with leads are acceptable without being mechanically secure in applications where the lead wires are not subject to movement after assembly.

# }7 B  d" q: eUL935
14.2 A soldered connection shall be mechanically secured before being soldered. The connection shall be insulated unless the spacings are in accordance with Spacing of Electrical Parts, Section 19.
; W% }9 o0 @( U# T/ h* b+ ^/ `. TException: If mechanical security of a soldered joint is impractical or impossible, a joint may be made without mechanical security before soldering, provided both sides of the joint are secured in such a way that stress on the connection, either during or after manufacturing process, will be unlikely.
1 |5 J3 L" P+ [" ?UL1993要求焊接件必须要机械固定后才算可靠的连接，但是SMT部件如果小于13mm，是不需要满足此要求的。
UL8750干脆一句话就确定，SMD不需要机械固定。
5 |3 L- s0 k' P8 I
留个议题，很多IC其实是大于13mm，但也是SMT部件，如何考核此类问题？
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# J0 N, d* O! C9 s欢迎讨论。

Liu

什么是机械固定？
+ J) z' n5 |8 |) n$ D$ kUL1993：
- U# H* Q# V1 ~- N+ w6.2.3 A wire is considered to be mechanically secure when one or more of the following is provided:
" `9 o! N1 E2 U3 ?" A, Ra) At least one full wrap around a terminal,
# C( L8 Q4 f+ ?, I! A8 `3 s$ lb) At least one right angle bend when passed through an eyelet or opening, except on printedwiring boards where components are properly inserted and soldered or mechanically secured
4 ^0 y. T& k5 Z* U9 P2 tby design, and
6 p5 z6 @* \# v$ [c) It is twisted with other conductors.
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a、端子绕一圈；
2 w7 W" a# S$ K: e/ }) k! c; W' wb、穿过开孔一个直角，PCB只要求穿过即可并焊接；
8 T  q* d* e# }0 Z9 S, y7 `: Kc、与导线相缠绕。

jxcyf

学习一下，期待高手的解答

sounnyday

分享个人想法…

) `- e' X( A* x# Z若是要小于13mm, 现在市面上SMD type 的power module 不就惨了!!
/ L# z5 ~3 [; z" n/ v6 ?
! J4 A9 h0 y" r0 V$ RSoldered connection应该不是指这方面的零件吧!
6 a6 f$ U6 n; a应该像是跳线, 地线(Grounding)的连接..
之前在申请UL 1283 EMI filter产品认证时, 就被要求Grounding 部分要有
. _  o5 k" Q/ k0 p4 dMechanical secured, 单只是焊锡是不足的, 最后把case修一个凹槽, 让地线可以绕一圈, 再加焊点就通过了!
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, Z7 t+ X; U+ x/ \. n: c# ]% m, h以上个人经验供大家参考!!

Liu

引用第3楼sounnyday于2010-07-08 13:12发表的  :
! R5 T% B2 f, M: q分享个人想法…

7 e3 x2 b6 @0 v4 }0 u! e# Y9 L若是要小于13mm, 现在市面上SMD type 的power module 不就惨了!!
; \- g, S/ Q0 y$ P: i( C
& w: y2 m8 h' _9 V7 |应该不是指这方面的零件吧!
& f0 _, l6 k3 g.......

. s) W4 F, w5 xSoldered connection指的正是焊接方式。关于IC，它有多个焊接脚，是否可以认为是机械固定？