We encounter many hurdles when developing an efficient, reliable soldering process. But, sometimes, getting over the first hurdle can make the next one more difficult.
For example, using a Pb-free SAC (SnAgCu) solder alloy in place of a lead-bearing alloy makes your reflow temperature go up slightly. But, 1) you have components that cannot withstand the higher reflow temperatures and 2) you have shock testing or other reliability tests that your device must pass. Now what?
There are excellent options that you can consider in the 115°C to 180°C temperature range. In fact, there are several alloys with reflow temperatures below 115°C that can be made into solder preforms. Whether they are bismuth-based or indium-based, contain Pb or are Pb-free, you do have choices!
One of the foremost experts in the soldering field, in general and in low-temperature solder specifically, is Dr. Ning-Cheng Lee. He will be giving a webinar on Tuesday May 17th and Thursday May 19th entitled "It's Time for Low-Temperature Solders: New Developments and Their Applications". The webinar is sponsored by SMTA. Check it out!
If you have questions on low-temperature soldering, please let me know at firstname.lastname@example.org and I will be glad to help!