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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Phil B

#10126

Component solderabilty | 16 August, 1999

We have a design on which there is an ASIC that will not be produced anymore in the future. As we want to make this design over the next 10 years we are evaluating the possibility to buy the necessary ASICs for the next 10 years. This will give us a solderability problem! Is there any way we can stock these ASICs so they will be solderable in 10 years time?

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Earl Moon

#10127

Re: Component solderabilty | 16 August, 1999

| We have a design on which there is an ASIC that will not be produced anymore in the future. As we want to make this design over the next 10 years we are evaluating the possibility to buy the necessary ASICs for the next 10 years. This will give us a solderability problem! Is there any way we can stock these ASICs so they will be solderable in 10 years time? | What is the package type, leads or balls, and metallization?

Earl Moon

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Scott Cook

#10128

Re: Component solderabilty | 16 August, 1999

| We have a design on which there is an ASIC that will not be produced anymore in the future. As we want to make this design over the next 10 years we are evaluating the possibility to buy the necessary ASICs for the next 10 years. This will give us a solderability problem! Is there any way we can stock these ASICs so they will be solderable in 10 years time? | I know this is in left field, but you don't give a lot of detail. I once worked for a firm who was in a similar quandry. They had outsourced the design and fab of the ASIC to a wafer fab facility in the pacific rim.

We negotiated a sale of the rights to the wafer. That way, we could incorporate any new packagaging as it came along......

Scott Cook scook@nettally.com

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Mark Thaler

#10129

Re: Component solderabilty | 16 August, 1999

| | We have a design on which there is an ASIC that will not be produced anymore in the future. As we want to make this design over the next 10 years we are evaluating the possibility to buy the necessary ASICs for the next 10 years. This will give us a solderability problem! Is there any way we can stock these ASICs so they will be solderable in 10 years time? | | | What is the package type, leads or balls, and metallization? | | Earl Moon | To insure solderability of components, heat seal the components within a nitrogen atmoshere. For information on this feel free to call me at 610-362-1320

Mark Thaler EMPF Helpline

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Brian

#10130

Re: Component solderabilty | 17 August, 1999

| We have a design on which there is an ASIC that will not be produced anymore in the future. As we want to make this design over the next 10 years we are evaluating the possibility to buy the necessary ASICs for the next 10 years. This will give us a solderability problem! Is there any way we can stock these ASICs so they will be solderable in 10 years time? | Hi

There are advocates of both vacuum and nitrogen. Unless you seal them in a REALLY hermetic enclosure, and this excludes all plastics over 10 years, neither will be OK. Better to store them normally and foresee a solderability restoration with a suitable dip and wash before assembly, IMHO.

Brian

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Glenn Robertson

#10131

Re: Component solderabilty | 17 August, 1999

| We have a design on which there is an ASIC that will not be produced anymore in the future. As we want to make this design over the next 10 years we are evaluating the possibility to buy the necessary ASICs for the next 10 years. This will give us a solderability problem! Is there any way we can stock these ASICs so they will be solderable in 10 years time? | Phil - The suggestions for vacuum or Nitrogen storage are good for reducing surface oxides, but if your package has copper leads with Sn or SnPb finish you will also eventually have a problem with CuSn intermetallics growing from the lead-to-plating interface. These will consume the available Sn until they reach the surface and affect the solderability. The process is dependent on time and exponentially with (absolute) temperature. Most soldering reference books can help you with this. If I'm wrong here, some of you old-timer metallurgist types please correct me.

Glenn Robertson

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Brian

#10132

Re: Component solderabilty | 18 August, 1999

| | We have a design on which there is an ASIC that will not be produced anymore in the future. As we want to make this design over the next 10 years we are evaluating the possibility to buy the necessary ASICs for the next 10 years. This will give us a solderability problem! Is there any way we can stock these ASICs so they will be solderable in 10 years time? | | | Phil - | The suggestions for vacuum or Nitrogen storage are good for reducing surface oxides, but if your package has copper leads with Sn or SnPb finish you will also eventually have a problem with CuSn intermetallics growing from the lead-to-plating interface. | These will consume the available Sn until they reach the surface and affect the solderability. The process is dependent on time and exponentially with (absolute) temperature. Most soldering reference books can help you with this. | If I'm wrong here, some of you old-timer metallurgist types please correct me. | | Glenn Robertson | Glenn

You are not wrong. Au contraire, you are right. However, SnCu intermetallics are not necessarily prohibitive, provided that the surface is activated. IMHO, what is worse is that the formation of SnCus will take place in tin-depleted matrix and the oxidised lead resulting is a real bugger. This assumes the substrate is copper and not FeNi alloys (e.g. Kovar). I have, on occasion, used 10 year-old components which have not been stored in any special environment and the problem is not too severe. In the good old days when it existed, Lonco made a product called Copperbrite, based on an aminosulfonic acid with much surfactant, I believe. It was a wizard for restoring solderability but hellishly difficult to rinse off afterwards.

At the very worst, a pre-re-tin will work wonders. Sorry for the neologism, but I think the hyphens make it clear :-) However, there is an additional word of warning necessary. Can we be sure that tin/lead soldering will exist in 10 years??????????????? Will your package be compatible with whatever you decide should take its place?

Best regards

Brian

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Phil B

#10133

Re: Component solderabilty | 23 August, 1999

| | We have a design on which there is an ASIC that will not be produced anymore in the future. As we want to make this design over the next 10 years we are evaluating the possibility to buy the necessary ASICs for the next 10 years. This will give us a solderability problem! Is there any way we can stock these ASICs so they will be solderable in 10 years time? | | | What is the package type, leads or balls, and metallization? | | Earl Moon It's a QFP240, SnPb metallization

Phil B |

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