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topic 6556

Drilled hole cleaning technology


I am working on future technology but have a small issue in cleaning drilled holes. The material I am drilling is a printed circuit board copper and fiber glass sandwich. due to the high temp while drilling the fiberglass and copper is plastered in the hole and also loose fiber inside the drilled hole creating a problem in plating and also the hole is clogged with the resin paste (due to high temp). Panel size 21" x 27" thickness 0.250" and a hole diameter of 0.010". My question is how can we clean the drilled hole? How can you help me? I have tried high pressure air knife, vacuum, ultrasonic cleaning and high pressure rinse. I would appreciate your help. Thanks

Bheemaraj Allaka
Sanmina Phoenix - phoenix, Arizona


First things first. Your problem is essentially one of drilling and possibly lamination, not cleaning. Work with the drilling and lamination to reduce the drill smear. There are some techniques to drilling high aspect ratio holes that the drill people have developed. Then use a good permanganate desmear process, possibly horizontal with ultrasonics. Finally, you might try a 10 second dip in warm, concentrated sulfuric acid with agitation prior to desmear as a LAST resort.

James Totter
James Totter, CEF
- Tallahassee, Florida


This reminds me of an application I recently saw in a catalog. Here's an excerpt:

"Ultra-Grit Microabrasive Nylon Brushes are designed for ultra-fine deburring and cleaning of holes produced by micro drilling, but will not alter the diameter or surface finish. On power tools, these brushes use a side-wiping action. They can also be used manually. Ideal applications include aerospace and aircraft parts, computers and electronics, medical equipment, and hydraulic fittings. Four types of brushes are available:

from Osborn International, Cleveland, Ohio I hope this was helpful.

Dean V. Balocca
- Wichita, KS, USA


Hi Bheemaraj !

Drilling very small diameter holes in plastics is a helluva problem as swarf builds up, as in your case, except that you have ULTRA small holes !

I've got a few tips which might be of some help.

#1. Re heat build-up ... use a 'lubricant' which instantly cools, i.e., spray can holding a very quick drying solvent. This is a 2 in l approach as the coolant keeps the drill bit nice and cold and simultaneously the 'spray' cleans off the build-up of swarf on the bit. OK?

#2. After drilling the holes ... (and redrilling doesn't really seem to work at all, does it?), what then about using heat in the sense of a red hot tip of 0.0l0" diameter to purge the hole.

#3. This mode works for metals you CANNOT drill using conventional drill bits (i.e., Ni Cr Mo alloys used for jet engine turbine impellers). It's called sacrificial drilling and uses an electrode.

Cheers !

Freeman Newton
Freeman Newton
White Rock, British Columbia, Canada

March 28, 2012

Q. We are using trichloroethylene in Ultrasonic machine to remove the lapping paste and oil, which is used to remove the burrs from micro holes of 40 micro diameter to 100 micro diameters. A small issue is in cleaning drilled holes and the material I am drilling is a cup of platinum and gold alloy. My question is how can we clean the drilled hole? I have tried acetone and ether. Would appreciate your help. Thanks

Aarti S
- India

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