P‑N junction coating resins for diode assembly

Recent­ly, a cus­tomer using Shin-Etsu KJR-4013E, the indus­try-stan­dard for p‑n junc­tion coat­ing resins, asked if they could use the KJR-4013E at tem­per­a­tures of 500C for 10 min­utes. This because this was the sol­der pro­file used for sol­der reflow.

KJR-4013E is a flex­i­ble, mois­ture-cure sil­i­cone most often used as p‑n junc­tion-coat­ing resins in the man­u­fac­ture of diodes. Ask us for the Tech­ni­cal Data Sheet (TDS) for Shin-Etsu KJR-4013. The KJR-4013E is a sil­i­cone mate­r­i­al and as such can with­stand high­er tem­per­a­tures. 500C is indeed a very high tem­per­a­ture, and it will def­i­nite­ly not sur­vive long times at this tem­per­a­ture. The point and the ques­tion how­ev­er is if it will sur­vive a short expo­sure time of 10 min­utes at that temperature.

An approx­i­mate degra­da­tion tem­per­a­ture for the KJR-4013E is around 300C after which it degrades quick­ly in time. If the mate­r­i­al is not degrad­ed, then it should still be able to pro­tect the P‑N junc­tion. A good way to test for this would be, use a ther­mo­cou­ple in the oven to mea­sure the exact time and tem­per­a­ture expo­sure of the mate­r­i­al dur­ing your sol­der­ing process and then to run a ther­mo­gravi­met­ric analy­sis (TGA) on the sil­i­cone for this same time/temperature profile.

As shown in the graph (Note: this is NOT the graph for KJR-4013E), once a mate­r­i­al goes beyond a cer­tain point, it begins to degrade quick­ly, and the process is irre­versible. The point at which the degra­da­tion accel­er­ates is dif­fer­ent for dif­fer­ent mate­ri­als, but for non-sol­vent con­tain­ing sil­i­cones, this can be as lit­tle as 3–4% of weight loss. Keep in mind with this graph that the tem­per­a­ture ramp is 10C per minute (as shown in the Method), and so the total time to gen­er­ate THIS graph up to 450C was 45 min­utes. This will NOT be the case with a 10 minute sol­der process, even as it ramps up to 500C, but a ther­mo­cou­ple through the oven will tell this sto­ry much more accurately.

Please vis­it our web­site for more infor­ma­tion about junc­tion coat­ing resin sil­i­cones, our sil­i­cones for LED encap­su­la­tion or any oth­er of our spe­cial­ty sil­i­cone prod­ucts. You can also con­tact us for more infor­ma­tion on P‑N junc­tion coat­ing resin silicones.