Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Tape residue cleaner

Ashok Dhawan

#4492

Tape residue cleaner | 7 April, 2000

Can anyone suggest a cleaning solvent for removing silicon residue after K Tape has gone through 2 cycles of reflow soldering ? The solvent or cleaning method has to be compliant to IPC Standards - to be used for cleaning gold edge fingers - PCB assembly carried out with NC Flusx Soldering.

reply »

Chris McDonald

#4493

Re: Tape residue cleaner | 7 April, 2000

Kapton Tape should not leave a residue. But Ive seem cheap Kapton do that. Anyways I have gotten a stencil cleaner soldevent to clean off tape residue (Multicore has a good one) It will meet IPC.

Chris

reply »

#4494

Re: Tape residue cleaner | 7 April, 2000

Ashok: You should select and use low residue tapes. But ya know, ya go out and research a great tape and if yer not careful, the buyer will second source ya and (surprise) ya got residues again. We have found that

Lemme say this about Katon tapes: � They�re expensive, which has a big piece to do with why buyers (and bean counters) are always angling to find a cheaper alternative. � Everyone who can spell "tape" makes a Kapton tape. � Lots of the high-temp Kapton-type tapes have silicone based adhesives, because they can take the heat without leaving visible residue.

If your tape adhesive is silicone, you probably will never completely remove it from your board. Things you can try are: � Recommendations from your tape supplier. � A special degreaser that a supplier of car painting would have in stock. It is a normal procedure to remove silicone residue on a car before painting. � Water and Cascade dish washing detergent in a dish washer. (This works. It�s not one of my Walmart jokes.) � Dow Corning (517-496-6000) OS fluid line (OS-2, maybe) product.

Each of these present problems removing the cleaning residues that you will have to resolve.

Beyond that, many silicone based adhesives are loaded-up with ammonia. This resents big time problems for no-cleaners. I�ve rattled-on about that in peelable solder masks on SMTnet previously.

We try to keep silicone based adhesives, RTVs, thermal greases, plastic bags with silicone mold release, and what not out of our plant. They have demonstrated the following problems:

1. Silicone is removed by common solvent or saponifier cleaning systems. Depending on the amount of contamination concentrating in the wash tank, other product cleaned in the same system may have significant amounts of silicone residues. 2. Silicone can easily contaminate fingers, gloves, cots, mats, totes, bags and the like. In this case, any surface making contact with the contaminated part will spread the silicone. 3. Small hand clean pans of solvent used in low volume military applications increase the cleaning problem noted in #1 above. 4. Now with respect to silicones that set up hard (like bath tub or weather sealers), there is actually a leach test that one can do to determine the % amount of extractable free silicones.

The results of these contamination scenarios are:

1. Silicone contaminated areas can inhibit wetting of conformal coating with Type AR or UR materials. I won't speak for other coating types - no experience. 2. Wave soldering can be affected because silicone can inhibit wetting of the liquid flux, and the oxides are not removed and the solder has a harder time wetting. 3. Solder paste can be affected because silicone can inhibit wetting of the flux to some degree by providing a physical barrier. 4. Mechanical contacts can become isolated by silicone material flow. Silicones are incredibly good insulators.

Finally, Ashok, you aren�t messing-up your boards with the ESD generated by the tape are you?

Ta Dave F

reply »

SMT Custom Nozzles

SMT equipment