We experienced a similar problem some time ago with one of our tin
plating baths.  It turned out to be a problem with our rectifier.  When
we were running 550 amps DC we also had 250 amps of AC.  We found this
by using a clamp-on probe which is connected to a DVM.  When the DVM is
in the VDC position we read 500 amps. In the VAC position, we read 250
amps.  Normally we would see less than 25 amps AC.  This is easy to
check and worth a try.  In our case, the tank chemistry was right were
it should be and the Hull cells always came out perfect yet the tin was
not uniform in appearance.

Hans Rohr

[log in to unmask] wrote:
>
> Hallo all;
> I need help to solve the problem of Tin/Lead peeling off during ecthing process.
> Tin/Lead alloy is used as ecth resist in our pattern plating line utilizing
> LeaRonal Plutin LA process. The plating time is 7.5min. and Current Density is
> 1.8~2.0A/dm2, then the resist layer is about 6~8um thick. Seldom did we find
> poor plating after pattern plating. But just after ecthing, you can see copper
> exposure in some pads or circuit, sometimes it is even worse to find open
> circuits or pin holes. The ratio of this kind of problem(referring boards) is
> about 3%. Sometimes when we do Hull Cell, the test panel looks dark in high
> current density area, sometimes it looks quite good. But the problem happens all
> the same. Also we have checked the PH and Cl content of etch solution, it seems
> OK.
> Can anybody offer suggestions to eliminate this problem?
> Thanks in advance.
>
> Ji Jiancheng

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet 
################################################################
Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311
################################################################