| | We have problems with voids when we solder lids to | | ceramic flatpackages. | | The sealring of the package is gold(100 micro inches or 2.5 micro meters)with a underlayer of Nickel | | The solder is attached to the lid (preform) and the solder material is Au/Sn (80/20 %) | | The package is heat treated twice before the soldering | | process. | | 1) Die adhesive (Silver-glass) hardening | | 1 hour and 45 min. | | Time above 350 deg.Celsius 15 min | | 2) Heat treatment in IR convection oven for | | 10 min. temp 370-420 deg. Celsius | | All heat treatments are done in Nitrogen atmoshere. | | The soldering process is done as recommended by the suppliers ( total time 30 min. and time over 280 deg. Celsius 4-5 min.) | | The flat packages and lids are stored in Nitrogen | | Does anybody know if there a risk of Nickel diffusion | | through the gold layer of the sealring ? | | Does Plasma washing/etching improve the soldering result ? | | Does anybody have any suggestions or recomendation | | I would be greatful !! | | Best regards Joakim Fagerlund | Joakim, | Thermocouple that component. It sounds to me like you have a problem with your profile for this application. You are using IR so the package is going to suck a lot of heat. You are also soldering with silver to gold. that requires an immense amount of heat in it's own right. find out what this assembly can take for a maximum temperature. It may be worth it to drill through a lid and insert a thermocouple. I suspect that the assembly isn't getting hot enough to form a good solder joint with all of the noble metal. Perhaps the plasma etch is a good idea but only etch the gold. Don't etch the lid. After etching, you're going to need to process immedeately as the oxidation window for exposed Ni is extremely short. just a few ideas. | Regards, | Justin Medernach Justin, I agree with all you say except it is very risky, as you point to the short oxidation window for Ni (very high, immediate oxidation rate), to even attempt soldering at this level. Soldering to Ni is unacceptable. With micro inches gold over whatever amount Ni should see little diffusion of the type that would be deleterious to solder joint formation. When soldering any type ceramic, it almost becomes a brazing or welding process because of ceramic's insulative characteristics. As Justin says, get the facts and adjust temperatures accordingly. You will require much heat to do this job. Can you use other sealing techniques as epoxies or glass to metal seals or? Earl Moon
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