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SN100C: High Temp

Views: 1809

theSaint

#39224

SN100C: High Temp | 19 January, 2006

I've seen many comments in many threads about the positive attributes of SN100C (apparently mostly by salesmen).

However, I have a concern for the higher temps that will be encountered when using SN100C (or Sn/Cu) vs. SAC305 (vs. 63/37), specifically for wave apps. I've already encountered multiple issues with temperature limits of electronic components (not to mention PCBs). Have you? When comparing SN100C vs. SAC305...is an extra 7-10 degrees a big deal? How has the electronics industry been dealing with this issue?

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George

#39236

SN100C: High Temp | 20 January, 2006

Hi "theSaint",

We are using SN100C in our wave solder machine. As far as the solder itself, the wave process follows pretty much the same concept as leaded solder. You bring the assembly temp to 90 C or more before the actual wave. Sometimes for multilayer and heavy assemblies the preheat temp should be brought up 120 C to see good solder fillets.

I think if you really have a "lead-free ready BOM" you should not deal with any temp issue. Also if you have identified temp sensitive components, you might think of using selective pallets and problem solved.

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#39239

SN100C: High Temp | 20 January, 2006

The temp is not an issue with selective soldering as the SN100C can be used at the same temp we used for tin lead. 260C. Some are using a higher temp, we did not notice any difference in the results with a higher temp.

Most people run thier waves at 500F, thats 260C. Remember, the entire component does not hit that temp for extended time like in a reflow oven. We do not have our wave running yet with SN100C but I would think it would be fine at 500F. I will let you know in a week or two. What temp do you run at George?

Also, this may not be the subjet at hand but,

I have heard some people make comments that SN100C is only acceptable for low reliability/low cost applications and that SAC305 is the choice for high reliability. I have seen no data to support that at all. SN100C is less expensive, that does not mean it is less reliable. Lets keep in mind where we all came from, tin/lead, very cheap, worked great. Just because something costs less does not make it inferior. We tried both and SAC305 creates way too much dross in a selective solder machine to make it practicle to use.

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George

#39245

SN100C: High Temp | 20 January, 2006

adlsmt, Solder pot temp is set to 265C. About solder joint quality, you must take in consideration the PCB finish when testing different leed-free alloys. Our PCB's are ENIG.

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