Test methods and influencing factors for the adhesion strength measurement of metallized structures on thermoplastic substrates

The requirements that apply to mechatronic systems regarding integration density, functionality, and miniaturization are significantly increasing. In this context molded interconnect devices (MID) offer in many cases an appropriate solution due to their spatial design freedom and versatile possibilities for functional integration. Already today, the technology is used in a wide range of application fields. Especially in safety and security relevant systems, the reliability is a crucial aspect, which is highly influenced by the adhesions strength of the metallized structures on the substrate. However, general standards or guidelines for testing MID do not exist and conventional test methods are in most cases only limited suitable for determining the adhesion strength of the metallization on molded interconnect devices. In this paper, commonly used adhesion tests are presented and assessed regarding their suitability for their use in MID. Thereby, the new hot pin pull test is introduced in detail. Comparative investigations with conventional test methods show promising results concerning reproducibility and a low standard deviation. The impact of influencing factors on the test results, such as the temperature or the wetting of the test structures with solder illustrates the importance of testing standards.