The world of epoxies is a continuously growing and changing environment. There are so many
decisions to be made in order to find the best solution for your microelectronics assembly applications. Here are some of the right questions to ask when it comes to deciding which epoxy to use:
Conductive or Non-Conductive?
The first decision point is whether to use conductive or non-conductive epoxy. You don’t want to use a conductive that will short between electrical contacts, and you cannot use a conductive to make an electrical connection.
Conductive epoxies typically achieve their conductivity through small metal spheres/flakes. Silver is the predominate metal and in probably more than 95% of the epoxies available today. Some epoxies can run 70% silver or higher. The major uses of conductive epoxies are to eliminate soldering on temperature sensitive devices, repairing PC boards, attach and connectivity of back-side metalized devices such as LEDs, gold bump interfaces, and many more. Some other benefits of conductive epoxies are that they are typically also thermally conductive, and they can even provide electromagnetic interference/radio frequency interference shielding.
Non-conductive epoxies can be anything from super glue to the thick, rubbery, silicon compounds you see in appliances and automotive applications. In microelectronics assembly, non-conductive epoxies are used for mounting die/components, underfill, and glob top applications. While they can be non-electrical connecting, they can still be thermally conductive. There are a wide variety of epoxies to choose from.
Cure Time and Temperature?
Again, there is a variety of all types of epoxies, for use from room temperature to 300C+. This is very important to address in the initial process/application phase. Bond times can also vary from “snap cures” in less than 2 minutes at 300C to day-long cures.
Bond Lines Desired?
This can be critical in micro-assembly since it factors in viscosity and characteristics of the epoxy. The method of epoxy dispense can also be a huge factor in bond line. Palomar offers a variety of methods from time pressure and auger, to digital dispense and daubing.
Working Time?
The basic question here is how long the epoxy can be used before it starts to change. This can vary from less than 10 minutes to over a day. This can also determine the type of dispense method used and the clean-up process required.
Of course, there are many other factors that can come into play, such as structural integrity and out-gassing, but the above are some of the important questions that should be answered before testing out an application with epoxy.
Would you like to learn more about epoxy? Read our blog on Automated Epoxy Die Attach, or download the eBook:
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Dale Perry
Regional Account Manager, Eastern Americas
Palomar Technologies, Inc.