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Tech Seconds: What is a Shoulder Reflow Profile?

Indium Corporation’s Tech Seconds video series features Phil Zarrow answering the electronics assembly industry’s most commonly asked questions... in less than 60 seconds. In this installment, Phil describes when to use a shoulder profile.

Question: Hey Phil, I'm familiar with ramp-to-spike and soak reflow profiles. What is a shoulder reflow profile?

Phil Zarrow: The shoulder profile was developed by Dr. Ning-Cheng Lee, the Vice President of Technology at Indium Corporation. What we have here is essentially a straight ramp profile, but we've added a very short soak zone. Typically, somewhere in the vicinity of under 30 seconds, and approximately 15-20 degrees below the liquidus temperature of the solder alloy.

Question: Why should I use a shoulder profile?

Phil Zarrow: The shoulder profile has been attributed to reducing tombstoning, as well as promoting better wetting. The idea here is that we're making sure that the whole assembly crosses over into liquidus at the same time, therefore, reducing our Delta T at peak.