|Ask the Experts|
April 17, 2020
Contamination From Anti-static Foam
Due to the rarity and value of this board, I want to preserve it and ensure it will still be operational. It has been suggested that a 90%+ isopropyl alcohol soak for the entire board followed by bruising with a soft toothbrush is recommended. Do you have any other thoughts on how best to tackle this problem?
|Expert Panel Responses|
I would suggest to go with 99% isopropyl. It's more expensive but works well.
Use fresh isopropyl or denatured ethanol and let the board dry in a warm oven to drive off any alcohol that might be stuck under parts. Should work fine.
Take care of components which might get damaged during full dip on this board. Use anti-static brush.
Many of the pink poly materials from that time era were doped with various amine complexes to provide the static protection. I suspect that is the case here.
Your solution may work, but I would use 50/50 isopropanol / water. If that does not work, try 10% methanol and 90% deionized water.
Principal Materials and Process Engineer
Yes, 70% or higher IPA with mild brushing should do the trick. If not you can get some CPU thermal compound remover followed by IPA. Be sure it is dried fully and then plastic wrap it.
President and Founder
A soak in IPA will only be useful if the material is soluble in a polar solvent which it may not be based on the material used and its age. You would also need to ensure that the parts on the assembly are suitable for immersion in a solution although again based on the age of the parts, this assembly was probably vapor cleaned post soldering.
You might want to consider a dry ice vapor cleaning method as a safe and efficient alternative to a soak and brush.
S T and S Testing and Analysis
Without knowing the types of materials on this board, it sounds like the advice you have been given is good. I would only suggest several immersions with fresh 90% alcohol. In this photo I cannot see a conformal coating.
Your chief concern is probably ionic contamination, which could short out the runs or leads on the chips. So, prior to firing up the board, make a careful inspection of the component leads to ensure there is not bridging of some type of foreign substance that could short it out.
Since you mention this is a high value PCBA and you want it to remain operational, your best option is to have the residues analyzed to determine the best solvent without affecting your board.
Senior Manufacturing Engineer
I would suggest DI water Steam with hand controlled wand. The foam has decomposed and the grounded steam line will allow both mechanical and thermal removal of the foam particles. If you are interested we can talk about how we can do this for you.
President/Senior Technical Consultant
Your question involves two steps:
Step two, once we know if organic or inorganic in nature we can then select chemical solvent (e.g., Alcohol, Surfactant, Saponifier, terpene, etc.), plasma ( e.g., Argon, Oxygen, etc.) and/or subsequent mechanical cleaning ( e.g., burnish, wipe, brush, etc.).
You don't state what the end application the assembly operates in ( e.g., IPC Class 1, 2, 3) for subsequent Ion Chromatography (IC) limits for verifying truly clean via Anions, Cations, and WOAs remaining to eliminate metal migration due to surface Ionics left behind.
VP of Advanced Technical Operations
Before soaking the whole board I would look to try any cleaning solvent you try to se on a small area that is not as important as ICs etc.
Either use a cotton bud soaked in the solvent or a lint free tissue soaked in the solvent and a brush. With the tissue method have the tissue between the brush and the residue, this will stop the brush soaking up the residue and spreading it to other areas of the board, unless you have lots of brushes and can throw them away as soon as the brush is contaminated.
The IPA solution is probably cheapest, but there are other cleaning solutions available from hobby stores and people like RS or tool station. As the board is old the residues are certainly natural rosin from the fluxes used combined with whatever else they have collected these should easily clean off.
Global Product Champion
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