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Conversion from SAC305 to SN100C

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#57981

Conversion from SAC305 to SN100C | 4 February, 2009

Hi All

We intend to switch fro SAC305 to SN100C, which has been giving us great test results. Unfortunately we have a technical guy at head quarter, which refuses to accept the SN100C as it has a 10 deg C higher melting point as SAC. I argue besides all the other benefits SN100C has that nobody is soldering at the melting point. How can we overcome this silly arguments? Has anybody of you ever had to make a case for the switch?

Thanks for your input Smartasp

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#57987

Conversion from SAC305 to SN100C | 4 February, 2009

Hi,

I have done conversion from SAC387 to SCS7 with great results on process improvement with low cost. I see only the melting point is higher but still the solder pot temperature settings is 250�C to 260�C as SAC. If somebody think the temperature is high for the board that is wrong because you still have to keep delta "T" in between 100�C to 130�C with setting up the temp-profile for single sided,double sided & multilayer boards. See here http://www.nihonsuperior.co.jp for more info.

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#57989

Conversion from SAC305 to SN100C | 4 February, 2009

Hi

The issue is not the equipment or any other technical matter. The point is that the argument is about the 10 deg C higher melting point. The process window of SN/CU is somewhat smaller but manageable. I know Nihons web site but found not enough info i.e. white papers available to make the case air tight. Cobar has also some good info on their web site.

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#57993

Conversion from SAC305 to SN100C | 4 February, 2009

It's not a silly arguement. I'm guessing you are talking about wavesoldering? Think about holefill, The reason tin will not fully fill difficult holes is the temperature at the top is too low, it is below the melting point. Increase this melting point temperature by 10deg and holefill will be worse, it makes perfect sence:

SAC has a melting point of 217, with the solderpot set at 260deg, you have a process window of 43deg. SN100C has a melting point of 227deg, decreasing your process window to 33deg, that is 25% less. That is a considerable amount imo.

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#57996

Conversion from SAC305 to SN100C | 4 February, 2009

We use SN100C in our selective solder process. The 3 keys to proper hole fill are applying a proper amount of flux, heating of the pcb and solder temperature. If either the pcb or solder is not hot enough, you may not get good hole fill.

To adjust for the 10C increase in melting point, you will need to increase the heating of your pcb and/or increase the temperature of your solder pot. In most cases, the increased temperatures will still be within the maximum soldering ratings of the components and pcb. FYI, we run a solder pot temperature of 285C which is well above the melting point of SN100C.

This gives the aditional point you can make which is that the components/pcb can handle the additional 10C temp increase and still be well within the process window for those parts. Not sure if that is enough to convince them but it might help.

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