I mentioned in the first blog post that I was excited to document my journey at Indium Corporation; it’s funny to think that most of that documentation has come from quickly scribbled notes during experiments and meetings instead of more structured writing as I had originally thought. When I look back at those notes, I realize there is a beauty in that form of writing. When a person is in the middle of conducting an important test or finishing a report for an important deadline, their mind is so focused on the task at hand. Then later on down the line, a more relaxed perspective allows that person to really take in what they’ve learned since that time. That’s true even if the immediate result of the test wasn’t 100% positive. Tl;dr your scribbles can mean something, so don’t crumple up your notebook papers from ages ago.
With all that being said, one of the important takeaways I’ve noted was the printing performance of no-clean and water-soluble solder pastes for semiconductor assembly applications. These two videos already posted on Indium Corporation’s blog do a great job explaining the differences between no-clean and water-soluble solder pastes, with the latter explaining the differences with regards to printing applications. Printing is especially important for semiconductor applications, with the ability for stencil apertures to be precisely designed for many shapes of solder deposits. Ed Briggs, Regional Sales Manager, explains that no-clean pastes tend to print better than their water-soluble brethren. He mentions that this could be because the rosin present in no-clean pastes does a very good job with maintaining a good roll of solder paste, and maintaining its shape upon release of the substrate from the stencil.
During my testing, I found this to be the case as well. What’s particularly important for semiconductor assembly applications is that the components to be soldered are very, very small. Since the components are so small, and more and more chips are being packed into a single die (did you hear IBM has developed a 2nm chip already?), the gap between these components is becoming smaller and smaller, some as low as 50 microns. For reference, that gap is just larger than one Type 3 solder ball, and manufacturers are placing solder pads that close to each other! Bringing this back to water-soluble vs. no-clean pastes, one can imagine the difficulty of cleaning between those tight pitches, and bridging issues become more apparent. So, choosing the correct solder paste for your end application in the semiconductor field is especially important. Indium Corporation, as a matter of fact, has recently announced a new SiPaste (system-in-package paste) that’s designated as “cleanable” instead of no-clean or water-soluble. Our new SiPaste C201HF offers the exceptional printing performance of a no-clean paste, but has a specially designed flux chemistry that enables the paste to be cleaned using a standard saponifier process.
If readers are interested in learning more about solder paste printing for SiP applications, I will be presenting a webinar on important printing parameters for SiP applications (SiP Printing 101, if you will). There will be one session at 8AM New York time on August 24th, and another session at 8PM New York time for August 25th, for the Asia audience.