DSH 710 Creepage/clearance

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广东安规检测
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DSH 710   ~. A  v. u: t5 Q) a; n! q 2 w; y1 b7 w1 a9 M# f, Z- _) r

Creepage/clearance ! g# N/ b) E, [+ ?+ z

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60335-1(ed.4) 5 z. e" U, b/ X$ b1 y& h3 H; P; y

  t* d2 H+ z2 E( C) cQuestion:
0 r$ @* `% {; q+ P7 r0 ?+ gWe have found situations in which a printed circuit board (PCB) with a declared CTI of 400 or higher, passes the test on the component side of the PCB, that is not lacquered, but does not pass the test on the printed circuit side with SMD components that is lacquered or varnished, and is typically in green colour.
& c1 l! \2 O2 \( o. X3 I4 t1 - Do both sides need to comply with the required CTI, if the corresponding creepage distance so requires it?
3 v0 J  ^# c9 Y0 T( F6 u  ?2 - On the other hand, it could be said that the varnish over the printed circuit side of the PCB allows us to consider that the creepage distance is not applicable. Therefore, the CTI would not be necessary. In our opinion, this consideration is not correct. Do you agree?
/ c3 `; e/ B+ W, Y+ d4 c0 i' e8 g% Z5 g3 - In any case, if the manufacturer wants to reduce the distances below the limits for the relevant CTI and pollution degree, the manufacturer could improve the pollution degree category by using a coating that is annex J compliant and apply the corresponding column for pollution degree 1 in tables 17 or 18. Do you agree?
7 S7 K+ u! f6 d" ?# a. e0 a4 - Even in the case of a CTI certified raw material PCB, the varnished side of the final mounted PCB should be tested to the relevant CTI unless a valid CTI certificate is provided. Do you agree?
9 q" f) k% r3 [5 A. f/ sDecision:
! S. e7 D  u) D: [7 N% W+ V% D( K1- If the varnish covers completely the PCB over the soldered components, no CTI is required for the varnish. CTI is required for the PCB under the varnish, and the corresponding distances must be required according to the varnish type 1 or 2.
( M% z# @1 ]2 v2- If there are relevant parts not varnished, for instance soldering points, the varnish has to comply with the corresponding CTI for the creepage distance in addition to the requirements under the varnish for the PCB.
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