Short and long term reliability of in-mould sealed bare and globtop shielded LED devices

In-mould integration of bare and glob-top shielded LED chips was demonstrated in an injection moulding process. The LED chips were first attached on conventional FR4 substrates and the substrates were used as inserts in the injection moulding process. Test series of 39 modules containing four green LED chips and 80 modules containing one blue chip were in-mould sealed using a polymethyl methacrylate (PMMA) polymer. When the holding pressure used in the injection moulding processing was 1000 bar or lower, 100% yield was obtained for the injection moulded LED modules. LED modules, which were operational just after in-mould sealing, remained operational after six months storage in normal office room conditions. Sealed LED long term reliability was estimated by accelerated environmental stress tests with elevated temperature and humidity. The test results showed that the in-mould sealing is a very promising manufacturing method for cost-effective module production. In order to get more reliable estimate for volume-production yield, however, larger series of test modules should be fabricated and tested. The required production tests are performed in the next phase of the manufacturing concept study.