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Wire bonding on gold fingers

Wire bonding on gold fingers

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We are currently producing a board for a customer that has a... - Jun 25, 2003 by Sr. Tech

I believe that Fancort makes some finger protectors that are... - Jun 25, 2003 by RDR

I need something that is very thin so I can screen print whi... - Jun 25, 2003 by Sr. Tech

SR. Here is a shot in the dark but have you try'd KNS? I kno... - Jun 25, 2003 by CAL

I've faced this several times in the past, and the only real... - Jul 01, 2003 by

did you check with lackwere peters? My frined told me that t... - Jul 02, 2003 by ramanandkini

Have you looked into Kapton tape as a protectant? ... - Jul 02, 2003 by T.E.A.M. Services

Have you considered a temporary water washable solder mask. ... - Jul 03, 2003 by

Use MicroCoat Technologies UV cure solder mask. will leave P... - Aug 02, 2004 by sforman1

If you do wire bond before printing, Photo Stencil (www.pho... - Aug 02, 2004 by John

Sr. Tech

#24955

Wire bonding on gold fingers | 25 June, 2003

We are currently producing a board for a customer that has about 400 gold fingers that get wire bonded after the assy. leaves our facility. We have tried many different approaches to ensure that we are not getting solder on the gold fingers. Nothing seems to be working consistently. We have quite a bit of experience with gold fingers, but this is turning out to be very difficult. What we would like to do is mask the fingers somehow, but our customer says that anything like Kapton leaves a residue and causes wire bonding issues. Does anyone know of any zero residue masking material ? Or any ideas on how we might approach this ?

Thank you.

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RDR

#24958

Wire bonding on gold fingers | 25 June, 2003

I believe that Fancort makes some finger protectors that are made of Metal (Aluminum, titanium, etc...) I don't know how well these would process through placement equipment however due to their thickness. Could you clean the Kapton residue off just prior to shipment?

Russ

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Sr. Tech

#24959

Wire bonding on gold fingers | 25 June, 2003

I need something that is very thin so I can screen print while the fingers are protected. We have tried cleaning the fingers prior to shipment, but our customer tells us that even alcohol leaves enough residue to cause problems.

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CAL

#24961

Wire bonding on gold fingers | 25 June, 2003

SR. Here is a shot in the dark but have you try'd KNS? I know they have been working on some cool polymers...send them a note as they may have something that meets your needs. They may not have anything that can be removed but it is worth a try.

polymers@kns.com or 215-784-7516

Cal

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jartman

#25028

Wire bonding on gold fingers | 1 July, 2003

I've faced this several times in the past, and the only real solution is to wirebond before SMT assembly. Everything leaves a residue, and trying to clean a residue off later is basically hopeless.

This may require some trickery in your SMT process, so that you can print solder over the glob-topped IC or whatever you're wirebonding. If this is very difficult, and the economics permit, you can use syringe solder dispense instead of stencil printing.

If it's really not possible to reconfigure your process in this way, your best bet is to clean any residue with plasma etching. This is not simply a matter of throwing it in the plasma oven with argon for 10 minutes - the residue you're cleaning will just be re-deposited (along with solder flux, solder mask, and PCB epoxy resin molecules) unless you get the process set up right with a reactive gas. You should expect to do some testing with surface spectroscopy to verify that the residue is really getting removed.

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ramanandkini

#25035

Wire bonding on gold fingers | 2 July, 2003

did you check with lackwere peters? My frined told me that they have some coatings for this application.

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T.E.A.M. Services

#25049

Wire bonding on gold fingers | 2 July, 2003

Have you looked into Kapton tape as a protectant?

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Ron

#25058

Wire bonding on gold fingers | 3 July, 2003

Have you considered a temporary water washable solder mask. Elvaway solder mask tapes have been protecting Gold Fingers during soldering and simply wash away in a water wash process and leaves no residue.

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sforman1

#29792

Wire bonding on gold fingers | 2 August, 2004

Use MicroCoat Technologies UV cure solder mask. will leave PCB absolutely clean. used in many PCB solder/wirebonding apps. http://www.m-coat.com

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John

#29793

Wire bonding on gold fingers | 2 August, 2004

If you do wire bond before printing, Photo Stencil (www.photostencil.com)can help you design a stencil with relief on the pwb side for the wirebonding.

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