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SMT electronics assembly manufacturing forum.


Solder on gold finger

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#42759

Solder on gold finger | 18 July, 2006

We are trying to reduce the number of unit fail at QA Visual Inspection due to Solder On Gold Finger. We know so far that the solder is spattering onto the Gold Finger during reflow. I need some advise on what kind of process can improve to reduce the defect

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#42772

Solder on gold finger | 18 July, 2006

kapton tape the gold fingers before reflow.........

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RDR

#42773

Solder on gold finger | 18 July, 2006

Clean up!, check all conveyors for paste, the printer, oven. If you are splattering in the oven than you need a better profile or better paste, one of the two, maybe both.

Hope was helpful

Russ

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#42777

Solder on gold finger | 18 July, 2006

How does your profile fit the paste manufacturer's specs? It sounds like you could be ramping up a little fast and boiling your non-metal constituents.

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#42789

Solder on gold finger | 18 July, 2006

Actually we run lead free solder paste and the profile spec very tigh.I can't use capton tape due my product in panel form and save cost.I already verify conveyor,machine and tool free from dust and solder paste but the problem still remain.

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#42791

Solder on gold finger | 18 July, 2006

Aping Russ' reply: * ~70% of the time solder on gold fingers is caused by poor printing and handling processes. * ~25% of the time solder on gold fingers is caused by poor thermal recipe when soldering. * ~5% of the time solder on gold fingers is caused by noseeums and whutnot.

Search the fine SMTnet Archives for further discussion.

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Francis

#42815

Solder on gold finger | 20 July, 2006

Short term, taped the gold finger. long term, study the air flow of the reflow section of the oven. It is always being overlook at this part and lookout for the printer. The air flow must be laminar and properly flowed back.

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#42817

Solder on gold finger | 20 July, 2006

If you are using SMT machine for component placement you may check your nozzle where in some cases solder paste stuck to it and during placement will easily get into gold pad area. otherwise you have use kapton tape in order not to expose those pads.

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#42819

Solder on gold finger | 20 July, 2006

We had a similar problem with gold contact pads. Cleanliness is paramount. If you are using foil tensioning system, wash the foil in a stencil wash before use as the cardboard cassettes may be contaminated. Be very careful when loading into a frame for the slightest bead of solder paste. Once washed, do not clean the underside of the stencil again. Switch off the underscreen cleaner. This contaminates the foil again which requires another wash. Talk to Qualitek about type 678 solder paste (UK number maybe). This is a low splatter paste with a UV tracer which was developed for such a problem.

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