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Ted Mooney, P.E. RET

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SLA plastics activation for electroless coating

Q. Hi there :)

I am a researcher in Europe involved in optical instrument development. I've been investigating PLD-SLA resins for complex parts that can't be produced with classic machining. I am especially working with the Somos PerFORM produced by Stratasys.

So far, I've been activating this resin using chemical etching with KOH before a Pd bath and electroless plating with NiP or Cu. I've been observing adhesion defects with a scotch-pull test from time to time.

I am looking to improve the etching phase: In the past, a documented approach has been to use a mix of sulfuric and chromic acid. This is out of the scope due to the very high toxicity of chromic acids and the European REACH regulation.

I would like to know if some of you have been working with this type of SLA resin and have tried to activate it. If so, with which products ? Do you have any advice ?

My approach is currently is to try several types of acids such as nitric acid, sulfuric acid and changing temp/time, and make SEM observations of the surface and droplet contact angle measurements.

Thanks a lot!
Have a good day all

Martin Lefebvre
Researcher - Marseille, France
February 20, 2025

Hydrofluoric acid burns

Never use HF anywhere unless trained!
If you do, you MUST have the antidote gel on hand for instant use!

Calcium Gluconate
for HF acid burns
calcium_gluconate

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A. Hi Martin.

The reason that ABS is the favored resin for plating onto is that it contains three polymers, one of which forms tiny balls which dissolve in chromic-sulfuric acid, leaving a sponge like surface for outstanding adhesion.

It isn't clear to me the constitution of Somos Perform, but it sounds like it has a high ceramic content such that hydrofluoric acid might be an effective etchant.

As far as I know hydrofluoric acid is not prohibited in the European Union, but it is way more dangerous than chromic acid -- don't use it except with calcium gluconate gel on hand.

Luck & Regards,

ted_yosem
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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