Keywords: indium, Indium Corporation, void, voiding, voids, Avoid the Void®, reflow, reflow profile, die-attach, die-attachment, thermal conductivity, Andy Mackie, diodes, triacs, solar
Phil Zarrow: This video is for engineers challenged by voiding in die-attach applications. It will cover causes and methods to Avoid the Void™.
Andy, what exactly is voiding as it relates to die-attachment?
Andy C. Mackie, PhD, MSc: Voiding in die-attach is the same as in any solder. It's a three-dimensional hole in the solder. It can occur in the bulk; it can occur on the edge.
Phil Zarrow: Now, as paranoid as everybody is in electronics, generally in assembly, about voiding, it's even more critical in die-attach.
Andy C. Mackie, PhD, MSc: Very much so. The mechanical aspects are there, of course, but there's more concern about the electrical and thermal conductivity reduction caused by an increase in the voiding. You'll see, for example, in discrete devices and small, separate-type devices, buck converters and so on, that the voiding criteria may be 5% single, 10% total. That's very common. You'll see that in a lot of diodes and triacs and so on. As you move to higher-voltage and higher-current devices, those that are used in solar energy, inversion, wind power, and so on, that voiding becomes much, much more critical. You'll see perhaps 2%, 1%, or even, in one customer instance, a 0.5% total voids allowed in this. The reason is pretty simple, that, again, the void reduces the conductivity – both electrical and thermal conductivity.
If you reduce thermal conductivity, you have heating within the junction, the circle TJ, that may be up to 150, 175, 200, as we move to wider band-gap devices with smaller die so that you get increased current density. As you increase the current, you get these heating effects, these circle Joule-Thompson heating effects. We've even seen, in one instance with a customer, where even with low voiding you pass a high enough current through the IGBT module, they will literally blow the die off the substrates because of the voiding.
Phil Zarrow: So, like everything else in our field, it's application-driven.
Andy C. Mackie, PhD, MSc: Very much application-driven.
Phil Zarrow: Andy, where can we get more information on this?
Andy C. Mackie, PhD, MSc: Let's recommend anybody to go to www.indium.com. We have white papers, information from Dr. Ning-Cheng Lee and his R&D team, and, of course, our famous blogs as well.
Phil Zarrow: Particularly yours.
Andy C. Mackie, PhD, MSc: Yeah.
Phil Zarrow: Andy, it's a pleasure. Thank you so much.
Andy C. Mackie, PhD, MSc: My pleasure. Thank you.