Additive manufacturing approaches for stress relief in semiconductor die packaging

Abstract

Packaging of semiconductor chips, especially MEMSbased, always causes stress on the functional areas of the die causing unpredictable changes in chip performance. As a consequence such devices can only be calibrated individually after complete assembly. Melexis and TNO have developed an approach to reduce significantly packaging stress effects by means of additive manufacturing of the die package. The device is calibrated in a standard package with a standard calibration tool whereas the client specific shape is realized with additive manufacturing afterwards. The placement of a dedicated nozzle onto a SOIC16 package with a silicon pressure sensor illustrates the approach. Additive M anufacturingContinued advances in material properties and processing speed brought micro stereolithography (µ-SLA) into industrial manufacturing. For specific geometrical requirements and/or small series (down to 1 piece), µ-SLA has become a costeffective alternative to mold based processes. The micro stereolithography technology is elaborately described in numerous publications, as e.g. in refs [1] and [2]. BackgroundThe manufacturing of 3D objects by stereolithography is based on the spatially controlled solidification of a liquid resin by photo polymerization. Layer-by-layer the product is built, thus allowing for maximum freedom of form. To produce a layer a light projector is used to illuminate a pattern on the surface of a resin with a controlled illumination depth. As a result of this, the resin in the illuminated pattern is solidified and a product layer is formed. Both laser based light systems and Digital Light Processing (DLP) are methods to illuminate the resin. In DLP a digital micro mirror device (DMD) is used, which projects a complete 2-dimensional pixel-pattern, so a complete layer of resin can be cured at once. This method minimizes processing time and allows for smaller pixel sizes than laser based stereolithography.