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soldering to hard gold plated PCBs

Mark Henebry

#12714

soldering to hard gold plated PCBs | 3 February, 1999

Does anyone know if I will have problems soldering surface mount components to an all hard gold plated PC board. We want to use hard gold similar to gold used for edge fingers because our customer is concerned about wear and conductivity of connector pads located in the center of the board. Selective gold boards are too expensive for this volume (50 boards). We've used soft gold,(5-10 microinches of gold over 150 microinches of nickel) for other SMT boards, but this board will be plugged in and out many times. The hard gold we've chosen is 50 microinches of gold over 100-200 microinches of nickel.The board has components only on one side. Any feedback will be appreciated.

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Earl Moon

#12715

Re: soldering to hard gold plated PCBs | 3 February, 1999

| Does anyone know if I will have problems soldering surface mount components to an all hard gold plated PC board. We want to use hard gold similar to gold used for edge fingers because our customer is concerned about wear and conductivity of connector pads located in the center of the board. Selective gold boards are too expensive for this volume (50 boards). We've used soft gold,(5-10 microinches of gold over 150 microinches of nickel) for other SMT boards, but this board will be plugged in and out many times. The hard gold we've chosen is 50 microinches of gold over 100-200 microinches of nickel.The board has components only on one side. Any feedback will be appreciated. | It's becoming a long day. Forgive me, but is 5-10 thick compared with 5-10 millionths". I just can't get it together.

Anyway, thin gold coatings, whether electroplated or electrolessly deposited, offer no problems with solder joint embrittlement. It's the phosphorous in the nickle bath that provides intermetallics that cause the problems. Look at all the discussion traffic on this subject. Ask Motorola. After all, they helped start this stuff.

Earl Moon

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Chris G.

#12716

Re: soldering to hard gold plated PCBs | 3 February, 1999

| Does anyone know if I will have problems soldering surface mount components to an all hard gold plated PC board. We want to use hard gold similar to gold used for edge fingers because our customer is concerned about wear and conductivity of connector pads located in the center of the board. Selective gold boards are too expensive for this volume (50 boards). We've used soft gold,(5-10 microinches of gold over 150 microinches of nickel) for other SMT boards, but this board will be plugged in and out many times. The hard gold we've chosen is 50 microinches of gold over 100-200 microinches of nickel.The board has components only on one side. Any feedback will be appreciated. | Have run into your same problem many times. Selective gold plating can be expensive at times. I agree. Used to build a product that had chip on board. Had exactly 50 microinches nonselective plating across the entire board. Had to have 50 microinches in order to produce good gold ball bonds. The solder joints were weak and grainy. The first side that was reflowed looked even worse after side two was reflowed. The yeild on this product was terrible. Finally switched over to uBGA. I would be very careful. Watch out for gold imbrittlement. I would do everything possible to lessen the cost of selective plating. Put buss bars on the circuit to make electrical connection to the gold fingers. Add tabs which get routed off. Have a test board made to test solder joint strength. Maybe even try gold compatible solder like Indium/Lead.

Hope you have better luck than I did.

Chris G.

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