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Graphite/Carbon deposit on PWB ( any Industrial Specs?)

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GSx

#58210

Graphite/Carbon deposit on PWB ( any Industrial Specs?) | 26 February, 2009

Hi

I am looking for informations/specs about graphite/carbon deposited on PWB as a "spring contcat" or land (? not sure how to say in English).

- Are there any Standards (IPC?)who define correct thickness of graphite ?

- Are there any Test Method to check for correct adhesion (bonding on PWB), hardness, electrical resistance of graphite ?

- other ?

Thank you

GSx

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#58280

Graphite/Carbon deposit on PWB ( any Industrial Specs?) | 5 March, 2009

There is no IPC specification on carbon ink.

Consider talking to your ink supplier to develop the proper quality definition that you require. Most suppliers have a good understanding of their product performance, for instance: http://www.coates.com/electro/circuits/news/connections/pcb.htm

Other carbon ink suppliers are: * Acheson Colloids Company 810-984-5581 * Grace Specialty Polymers 617-861-6600

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GSx

#58329

Graphite/Carbon deposit on PWB ( any Industrial Specs?) | 11 March, 2009

Thank you so much Dave,

by having different lots of PCB received (same Supllier) with suspected and good carbon ink deposit, I found useful to adopt a comparison test among the different lots by usingthe IPC-TM-650 2.4.1 Adhesion , Tape Testing (like).

The suspected deposit, after first pull came awy in a significant amount, and after 4 more test on same deposit site , more the 50% of deposit came away.

Same test has been performed on "good" Lot of PCB, a very little amount of carbon came away after first pull, almost nothng at secon.

We tested also another PCB from another supplier, nothing came away even at first pull. The shape of deposit was also better and well defined.

By those results well documented, it was easy to Claim against the PCB Supplier.

Thanks again

Best Regards..........GSx

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#58344

Graphite/Carbon deposit on PWB ( any Industrial Specs?) | 13 March, 2009

Hi GSX,

just and FYI on why you are seeing a difference per lots.

Carbon Ink is Not used on a steady bases by most manufactures, and shelf life of the Carbon ink is fairly short, my guess is what they are doing is adding thinner to the carbon ink to make it last longer before having to throw it away and buy new. At my last Company I worked for this was Normal practice. Problem is that to much thinner and the conductive ink will not hold its shape and will be thinner than it should be.

Have you ever thought of changing to Enig? I have two customers who make RF Radios that have switch to Enig and have had no issues with keys. Maybe something to look into.

Regards,

Boardhouse

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