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Golden Finger contamination with Solder after reflow

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#79321

Golden Finger contamination with Solder after reflow | 13 November, 2017

Recently we facing the Golden finger reject due to contamination with solder after the reflow. Any solution for this kind of reject ?

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#79326

Golden Finger contamination with Solder after reflow | 13 November, 2017

Preemptively you can apply Kapton tape to protect the gold fingers during reflow. I think that's what most people do.

After the fact, there are services available to clean them up but as it was described in another thread here, it is not in-expensive.

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#79327

Golden Finger contamination with Solder after reflow | 13 November, 2017

Determine the origin of the solder

* Sloppy paste printing technique

* Lax stencil underside cleaning practices

* Sloppy misprint cleaning practices

* Poor part placement practices creating solder balls

* Poor material control allowing solder paste to dry-out

* Aggressive reflow profile causing solder balls th be being ejected from paste deposit

* Filthy reflow oven with solder material dripping from the top unit

* Poor handling practices

Steve Thomas makes good suggestions in the above thread for containing the problem until you determine what's going on and making it stop.

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#79329

Golden Finger contamination with Solder after reflow | 13 November, 2017

Hi, thanks for reply. Kapton tape is costly and it may create another handling issue. BTW can you share the thread for the cleaning process ?

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#79330

Golden Finger contamination with Solder after reflow | 13 November, 2017

Hi David, thanks for reply We did doing some study, most properly this problem was due to reflow process. Any thing that we can do for the reflow profile ? slow down the ramp up rate or .....

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#79331

Golden Finger contamination with Solder after reflow | 14 November, 2017

If you think the problem is occurring in the box and it is wide spread, consider replacing your solder paste with your paste supplier. There are paste formulations aimed at the solder balling issue that some LF pastes create.

On tuning your reflow recipe with an experiment:

* If preheat ramp rate is too low, flux thins and leaks from the paste deposit and carries raw fine solder particles across the board.

* If preheat ramp rate is too high, the flux boils and ejects raw solder from the paste deposit

Snarky comment about cleaning Kapton tape adhesive reside:

* Kapton tape that you buy will not leave a residue

* Kapton tape that your buyer [or Roland] purchases will leave a residue

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#79333

Golden Finger contamination with Solder after reflow | 14 November, 2017

Yes, thanks for bringing up that point, DaveF. All polyimide tapes are not created equal, and in my experience Kapton has always worked for this application. The "better deal" has not, ever.

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#79335

Golden Finger contamination with Solder after reflow | 15 November, 2017

You don't clean contaminated gold fingers so much as you replace them. I once had the "cleaning" solution. It totally dissolved the gold fingers so that they could be replaced.

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