Trelic’s picture of the week 7/2018

Attaching flexible circuits to each other



Last week we discussed about polyimide in flexible substrates. This week’s picture continues with the same topic. In the picture above you can see two of these flexible polyimide circuits attached to each other with electrically conductive adhesive, forming a flex-to-flex attachment.

When flexible electronics are developed, they almost always consist of several different devices and structures. It’s vital to connect all these different structures to each other. And, when reliability is considered, interconnections are often one of the weak spots. Therefore, it is important to test these interconnections in critical environments.

This flex-to-flex attachment structure is one of our test structures. With this simple attachment with a trace width of 100um we studied the performance of various anisotropically conductive adhesives (ACAs) in humid environment. Despite the tendency for PI to absorb lots of moisture, our test structures had low and stable resistance and good reliability during the used high humidity test.  This kind of good reliability can, however, only be achieved when both the selection of the used ACA and the bonding parameters are optimized. There are a lot of differences between the adhesives and the principles of selecting suitable bonding parameters somewhat differ from those of rigid attachments.

Flex-to-flex attachments with ACAs and their reliability in humid environments are important topics for us this week (11.-12.4.2018): Laura and Sanna are in Berlin attending IDTechEx Show and Laura will share her expertise in the topic of flex attachments. If you happen to be in Berlin- let’s meet!