DSH 710 Creepage/clearance

小米

广东安规检测
有限公司提供：

小型摆管淋雨试验机

IPX5X6X7喷水试验机

1000L恒温恒湿箱

各种试验指现货

可程式恒温恒湿试验箱

水平垂直燃烧机

自动卷线器试验机

耐划痕试验机

各种灯头量规现货

灼热丝试验机现货

GB1002插头量规

IPX1-X7淋雨现货

IEC61347/UL935镇流器热试验箱

灯具防风罩

IK冲击试验机

UL498插头插座量规

VDE0620插头插座量规

稳定性试验台

家电温升测试角

针焰试验机现货

热电偶焊机现货

家电125mm试验指

E12灯头量规

无绳壶无绳电熨斗插拔寿命试验机

IEC60335试验指甲

DSH 710 & [7 {# a0 I( ?. U% t2 v1 g& J, p' X( ]

Creepage/clearance

29.2

60335-1(ed.4) 3 f5 W$ t( e* L0 ]. `. M0 T

Question:
We 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.
+ y! W4 H2 {( e1 - Do both sides need to comply with the required CTI, if the corresponding creepage distance so requires it?
: n+ ~! M# t, ^" D  V2 - 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?
, U+ U- V2 w: v7 n3 - 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?
4 - 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?
7 w2 L, I. V1 L( UDecision:
1- 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.
8 L6 v9 k8 v  p7 {- t0 `2- 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.

, p1 g" p( ?' G5 O7 ~( K) X
" U: ?( l) s& f) k4 K3 I+ T/ l; `