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Can Tape Residue Contaminate a Clean Tank?



Can Tape Residue Contaminate a Clean Tank?
We leave masking and Kapton tapes that fall off during cleaning in the bottom of our wash tank. Can the adhesives contaminate the recycled solution?
Board Talk
Board Talk is presented by Phil Zarrow and Jim Hall of ITM Consulting.
Process Troubleshooting, Failure Analysis, Process Audits, Process Set-up
CEM Selection/Qualification, SMT Training/Seminars, Legal Disputes
Phil Zarrow
Phil Zarrow
With over 35 years experience in PCB assembly, Phil is one of the leading experts in SMT process failure analysis. He has vast experience in SMT equipment, materials and processes.
Jim Hall
Jim Hall
A Lean Six-Sigma Master Blackbelt, Jim has a wealth of knowledge in soldering, thermal technology, equipment and process basics. He is a pioneer in the science of reflow.

Transcript


Phil
And welcome to Board Talk with Jim Hall and Phil Zarrow, the Assembly Brothers, who by day go as ITM Consulting. Today we are in the clean room and we have a cleaning question Jim.

This is from J.H. Can adhesive residues from tapes contaminate a cleaning solution? We typically leave masking and Kapton tapes that fall off during cleaning in the bottom of our aqueous cleaning wash tank. Normally we would remove the scrapped masking and Kapton tapes once per day. Can the adhesives on the tapes in our tank contaminate the recycled solution?

Jim
Well, the basics of cleaning. Your solvent must match the soils. That means the solvent in your cleaning tank must be able to completely dissolve, emulsify, whatever all of the chemicals in your tank residue. If they’re not, they are going to float around or become globs. Also, if they’re not, are they cleaning the residue completely off of the tape and off of the board? So that you have a fully cleaned board.

Phil
I guess I am wondering why J.H. and friends are not removing the tape before cleaning anyway. Tapes are designed to strip clean. Why let it sit on the bottom of the sump there? It may not be doing any harm or adding to it but it is not necessarily doing any good.

Jim
Even if the solvent in the tank is completely compatible and is completely dissolving the adhesive, you’re overloading your solvent. You are going to contaminate your solvent. You are going to need to change your solvent more frequently because you are putting a greater cleaning load on it. You are putting more soil into the tank.

So why do that, even if it does a good job? I am trying to come up with an idea of why you need to leave the tape on into the cleaning system. Everything soldered is not holding anything anymore. Just strip it off manually. Get it out of there. Don’t risk contaminating your tank or reducing the life cycle of your cleaning solvents.

Phil
I am trying to think in my mind Jim, unless it is a fully automated line where the reflow oven is feeding directly into, or in this case the wave solder machine, is feeding directly into the cleaner. We don’t see that often these days. Usually the cleaners are in a separate area.

Jim
Well good luck, J.H.

Phil
You’ve been listening to Board Talk with Jim Hall and Phil Zarrow, The Assembly Brothers. Answering your questions about process and related things with surface mount and electronic assembly. However you are cleaning the board when you go to solder them, please don’t solder them like my brother.

Jim
And don’t solder like my brother.

Comments

I'd be far more concerned with the ability of the tape to clog filters or jets and then totally change the inline effectiveness since you have changed a key parameter, spray pressure across the full bar.
Eric Camden, Foresite
Much information missing from the question. So will make assumptions after 40 years solving problems for the Electronic Packaging industry.

Today's default cleaning fluid is hot water (140DF), with maybe a DI rinse. SO the adhesive will slowly leech into the water until the 'trash' on the drain screens gets removed. The polyimed will not dissolve in the water but will support fungal growth on the the 'trash'(slimy goop)! If there is a chemistry added then the possibilities of contamination and damage from the tape residue multiplies. If the residue includes the "Water-soluble" masking tape then the residue will become a stringy slimy mess if not cleaned/flushed at least weekly.
Ike Sedberry, Sedberry Sales Inc.

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