Letter 13064

Blister Problem 

Good day Sir,

At present we are having problems on our products, we are encountering blister or bubbling of the plated layer after the units were subjected to Temp Cycle with approx temp of -65 C and 150 C. The blister problem is not evident right after plating. One of our suspect is the stamping oil which is used as a lubricant to manufacture the frames. Result of our EDX analysis showed that the pricked blister samples has a high amount of carbon. While result of FTIR analysis showed that there was no difference in terms of carbon-chains between the blister-affected samples and those that were not affected. Signifying that the contamination from the samples are either already well spread or there were no contamination at all, since there were no difference. What do you think is causing this blister problem? Perhaps you could suggest some things that we could look into, and dig deeper on the causes of this problem.

Hopefully your staff could accommodate my inquiry. Thank you very much and best regards.

Nats Pogi
- Philippines

You haven't really told us anything yet, including what the substrate is, what cleaning and activation sequence you are using, or what you are plating it with! Blistering upon baking is not always due to some mysterious material leaching out, and can simply be that adhesion is marginal and heating emphasizes the fact.

Ted Mooney, P.E.  finishing.com Brick, New Jersey

It is very important that surface is clean before you start plating. Do you anodically degrease your product? Do you rinse it well after that? Do you give any acid dip before you start plating?

If hydrogen is trapped in base metal, then also you can get blister. Do you degas product at desired temperature before you plate? Try those alternatives and see if they help.

Good luck.

Payal Mag
- Charlotte, NC

In order to try to answer your question the following information is needed: What type of plating. What substrate. What is the finishing cycle.

Gene Packman
process supplier - Great Neck, New York

Attention: Ted Mooney, Payal Mag, Gene Packman

Sir's, thank you very much for replying to my inquiries. To fill in the holes in my letter here it is:

1. The substrate we're using is Cu, the material is CDA 151

2. As for the electrocleaning process, were using 30 g/l NaOH for the removal of organic contaminants and 22.5% Sulfuric Acid as our Activator Chemical. The dumping frequency for both chemicals is monthly. The effective length of cell is 1.5 m for Electroclean and 4.8 m for the Activator.

3. Yes we anodically degrease our product, and rinse it after that. We employ predip prior plating which is MSA at a concentration of 20%.

4. The plating line is strip-to-strip, as a finishing cycle, we have drag out rinse, neutralizer and Deionized Water Rinse, Blower and Drying.

Hoping for your immediate response. Thank you.

Nats Pogi
- Pasay City, Philippines

Dear Nats Pogi,

Blistering in spot silver plating of lead frames is almost always caused silver immersion plating onto the copper before the rectifier is turned on. Some suggestions are to increase the amount of anti immersion chemical in the silver bath. Decrease delay time between pump turning on and rectifier turning on. Pulse plating at 30 percent duty cycle is normal to improve silver uniformity adjacent to mask edges.

If there is any segregation of the Alloy 151 components, a copper strike helps provide a consistent surface for spot plating.

Good luck,

Pat Mentone St Paul, Minnesota

I think Pat gave you the right answer to the problem, but if not then if your cleaner is simply caustic soda, you probably should be using a proprietary cleaner with detergent in it. Also the cleaner may not be hot enough.

You must make sure that there is no silicone in the stamping area or used in the machinery as most cleaning cycles are not capable of removing it.

Pat Mentone St Paul, Minnesota

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