Michael: I've read your question but I'm having a little bit of a hard
time following it, so I'm going to ask you few questions and follow that with a
some inputs based on assumptions.
1. At what point are you seeing the voids; after electroless Cu, after
electrolytic Cu, after etch, etc?
2. Are you doing a backlight test after electroless Cu, If you are what did it
look like?
3. Are you doing a weight gain coupon on your electroless Cu, If you are what
was it?
4. Is the problem on multilayer boards, double sided or both?
5. Do you know if the problematic jobs/work orders were run back to back or at
various times during the day?
6. Are the boards in the same orientation in the electroless bath as in the
electolytic bath i.e. bottom side is always down?
7. Where are the voids, on the glass, on the resin, on the Cu, etc?
8. Do the voids appear in certain hole sizes large, small etc?
O.K. here goes the assuming: You talk about voids after electrolytic plating
but then talk about "cuposit". You then talk about the voids being caused by
mechanical issues which I'm not to sure of unless this carries over to the
problems with the pump and heater which actualy become chemical reaction and
tranfer problems. You then tie this back to the "cuposit". I"m assuming you mean
electroless Cu when you talk about "cuposit" which is a trademark for a variety
of Shipley electroless coppers.
With all that said it sounds like the voids are originating at electroless Cu
but not being detected until sometime after electrolytic plate.There's a whole
grocery list of what can cause this however based on your information about the
heater and pump problems I would guess the problem was slow iniation of the
electroless Cu plate,which can be seen as a rapid outgassing around the boards.
If this doesn't take place in the first 30+ secs of immersion in the electroless
bath you can start to loose the palladium catalyst sites which will result in
poor electroless Cu coverage. Temperature and bath chemical circulation, i.e.
heater and pump can greatly affect this. Time/temp/chemistry of your conditioner
and catalyst baths also play a critical role. Answers to the above questions
would also help to pinpoint possible problem areas.
Regards
Michael Barmuta
Staff Engineer
Fluke Electronics
Everett Wa.
425-356-6076
On Tue, 14 Apr 1998 01:55:11 -0700 MICHAEL DODSON wrote:
> From: MICHAEL DODSON <[log in to unmask]>
> Date: Tue, 14 Apr 1998 01:55:11 -0700
> Subject: [TN] Voids
> To: [log in to unmask]
>
> We are experiencing a problem with voids. The void issue tends to be
> on one end of the panel only, this end of the panel is towards the
> bottom of the electrolytic copper tank when plated. Voids have
> occurred on 4 different jobs all cuposited and plated on the same
> day, but not all the panels had voids and other orders went thru
> without voids. All chemistries were analyzed and found to be in spec.
> During this time period we believe that the void issues are
> mechanical. Low temp in cuposit or poor re-circulation due to pump
> problems. Any suggestions on what other items should be checked?
>
>
> Michael Dodson
> Product Engineer
> SBC Inc.
>
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