It is easy to conclude is that it is necessary for manufacturers of diodes, thyristors and other high power devices to determine the Shin-Etsu KJR-651E cure condition that gives the best characteristics of the polyimide silicone on customers devices. This is meant to act as a guide to optimize the process for many customers.
Our standard cure schedule recommendation for the Shin-Etsu KJR-651E is as follows:
150°C for 1hr + 200°C for 1hr + 250°C for 4 hrs
This is the minimum cycle required to drive out the solvents and get good cure characteristics. However, this is only a recommendation; a good starting point.
Some manufacturers use a hotter, longer cure cycle such as :
110°C for 1hr + 200°C for 1hr + 250°C for 8hrs + 300°C for 4hrs + 380°C for 30 mins.
It has been determined by them that this is optimum cure cycle required to maximize performance and minimize current leak. This has been confirmed by several customers who measure the gate leakage or leakage current at the maximum temperature of the junction test when the reverse voltage is applied.
These two cure conditions likely (but not definitely) represent the two extremes in cure conditions that customer could use to test the performance of their parts – especially to test for gate leakage at high temperatures. Though the higher temperature may give better gate leakage parameters, the standard may give better adhesion characteristics. Either way, these parameters ultimately need to be tested by the customer, ultimately testing both the adhesion characteristics and leakage current at the max temperature of the junction test.