Low-stress over-molding of media-tight electronics using thermoplastic foam injection molding

Due to increasing automation and the associated rising demands on electronic assemblies, a suitable manufacturing process for large-scale production is needed to protect such products. The big challenge in this context is the low-stress encapsulation of the assemblies to protect them from external influences. In this study, the foam injection molding process was used to encapsulate FR4 (epoxy-based PCB) with Polyamid66 (PA66). The focus was on the production of a good assembly in terms of the quality of the bond and the media tightness. These parameters can be used to evaluate the protective effect against the surrounding. In the tests, a leakage rate of 0.025 m/min and shear stress of 6.5 MPa was achieved at low-foaming rates. This leakage is below the maximum acceptable threshold of 0.5 ml/min. The shear stress reaches values comparable to those in injection molding In addition to the requirements for leakage and composite quality, it could be shown that the internal mold pressure is reduced from 450 bar to below 10 bar by foaming. This can be used as the first indication of a reduced shear load on electronic components during over-molding. The suitability of the new solution concept is demonstrated.

Automated summary

Foam injection molding process was used to encapsulate FR4 with Polyamid66 in order to achieve high-quality assembly production and protect against external influences. Successful tests showed low leakage rate and shear stress, demonstrating the suitability of the new solution concept.