Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

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Chuck Garth

#13509

Gold Finger Cleaning | 13 November, 1998

I believe that gold fingers on my circuit boards are being contaminated and need to clean them with some chemical solution. Any recommendations.

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Dave F

#13510

Re: Gold Finger Cleaning | 13 November, 1998

| I believe that gold fingers on my circuit boards are being | contaminated and need to clean them with some chemical | solution. Any recommendations. | Chuck: What is the type and source of your contamination? Dave F

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Chuck Garth

#13511

Re: Gold Finger Cleaning | 13 November, 1998

| | I believe that gold fingers on my circuit boards are being | | contaminated and need to clean them with some chemical | | solution. Any recommendations. | | | Chuck: What is the type and source of your contamination? Dave F | We are using a silicone uv cure for die wire bond encapsulant. also a kapton tape with silicone adhesive to protect fingers through wave solder. Also possible contamination due to oxidation through time.

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Kallol Chakraborty

#13512

Re: Gold Finger Cleaning | 13 November, 1998

| | | I believe that gold fingers on my circuit boards are being | | | contaminated and need to clean them with some chemical | | | solution. Any recommendations. | | | | | Chuck: What is the type and source of your contamination? Dave F | | We are using a silicone uv cure for die wire bond encapsulant. | also a kapton tape with silicone adhesive to protect fingers through wave solder. Also possible contamination due to oxidation through time.

Chuck:

I think IPC has some spec. on adhesive used for kapton (for masking/laminating [flex] purpose) tape. we had a lot of problem on the gold fingers as we were using normal 3M tape (yes ! from the drug store) for gold peel test which in turn leaves the adhesive residue behind, contaminating the fingers itself. Our rework process was to wash it with a non-aggresive cleaning solution (Isopropanol) (depents on your facility and cust. qual/cert reqrmnt.) and lint-free material. Level of contamination can be found out by using any method stated in IPC -TM 650.

An eraser can help you a lot but can be used only in moderation and is not recommended (in some facilities and application) for immersion gold or plating under 10 u inches.

Re-plating can be done by using any gold contact plating system(CEPS-connector edge plating system) can be found in IPC -R 700 or Circuit technology center - Document # CRC-20.

I think gold plating and surface cleanliness requirement spec for bonding (gold purity) is different than edge connector but dont quote me on that.

Hope that helps.

Regards Kc. | |

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Earl Moon

#13513

Re: Gold Finger Cleaning | 14 November, 1998

| | | | I believe that gold fingers on my circuit boards are being | | | | contaminated and need to clean them with some chemical | | | | solution. Any recommendations. | | | | | | | Chuck: What is the type and source of your contamination? Dave F | | | We are using a silicone uv cure for die wire bond encapsulant. | | also a kapton tape with silicone adhesive to protect fingers through wave solder. Also possible contamination due to oxidation through time. | | Chuck: | | I think IPC has some spec. on adhesive used for kapton (for masking/laminating [flex] purpose) tape. we had a lot of problem on the gold fingers as we were using normal 3M tape (yes ! from the drug store) for gold peel test which in turn leaves the adhesive residue behind, contaminating the fingers itself. | Our rework process was to wash it with a non-aggresive cleaning solution (Isopropanol) (depents on your facility and cust. qual/cert reqrmnt.) and lint-free material. | | Level of contamination can be found out by using any method | stated in IPC -TM 650. | | An eraser can help you a lot but can be used only in moderation and is not recommended (in some facilities and application) for immersion gold or plating under 10 u inches. | | Re-plating can be done by using any gold contact plating system(CEPS-connector edge plating system) can be found in IPC -R 700 or Circuit technology center - Document # CRC-20. | | I think gold plating and surface cleanliness requirement spec for bonding (gold purity) is different than edge connector but dont quote me on that. | | Hope that helps. | | Regards Kc. | | | | | | The difference for gold contact areas is the type used and the plating process used to apply it. "Hard" gold is used on contact finger areas. It oxidizes very little so the discoloration is copper leaching through a poorly processed nickel barrier as an intermetallic tha readily oxidizes. It cannot be cleaned. It can only be prevented through effective design and fabrication process management.

"Soft" or bondable gold is used elsewhere as in die attach and wire bond applications hence its name. Electroless gold is deposited in thicknesses not more that about 7 millionths" over electrolessly applied nickel (about 100 millionths") over copper for SMT solder termination areas.

Earl Moon | |

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