Accessible Unlicensed Requires Authentication Published by De Gruyter April 9, 2020

Joining of Contact Pins and Conductive Compounds via Injection Molding – Influence of the Flow Situation on the Electrical Contact Resistance

H.-P. Heim, F. Mieth, A. Schlink, K. Wiegel and L. Brabetz


While a lot of research can be found in the field of bulk resistance of carbon filled polymers, comparatively few papers focus on contact resistance between compound and metal contacts. Due to that small number of researches that deal with contact resistances, studies of the influence of injection molding conditions and parameters on the contact resistance are also very rare. In contradiction to that, these influences on bulk resistance have been studied. The objective of this work was to investigate the electrical contact resistance of overmolded tinplated copper contacts after modifying flow situations and molding conditions by procedural and constructional methods in contact areas. Metal pins were overmolded with a polypropylene compound containing 45 vol.% graphite, utilising an insert injection molding process. To affect the flow situation at the contacts, several processing parameters, such as mold temperature and injection speed, were modified. In addition, the contact alignment related to melt flow direction was varied. Electrical properties were studied and related to macroscopic and microscopic connection properties and flow situations in contact regions. It was found that the contact resistance is a significant factor while examining electrical resistances of overmolded samples. Furthermore, it was shown that the various flow situations had an essential impact on contact resistances. Weld lines at the position of the contact caused a decreased contact resistance. The correlation of the weld line effect, the filler orientation and contact resistance were successfully investigated by μ-CT. Regarding processing parameters, it was observed that a high mold temperature of 120 °C increased not only bulk conductivity, but also had a positive impact on contact conductivity. Macroscopic and microscopic connection mechanisms of contact surfaces were interpreted and connected to the experimental observations.

Mail address: André Schlink, Institut für Werkstofftechnik, Kunststofftechnik, Universität Kassel, Mönchebergstr. 3, D-34125 Kassel, Germany, E-mail:


1 Chen, S. C., Chung, C. Y. and Tseng, Y. L., “Effect of Magnetic Field on the Fiber Orientation during the Filling Process in Injection Molding, Part 2: Experiments and Electrical Conductivity Measurements”, Material Science Forum, 936, 36141 (2018) 10.4028/ in Google Scholar

2 Doagou-Rad, S., Islam, A. and S⊘ndergaard, J. J., “Correlation of Mechanical and Electrical Properties with Processing Variables in MWCNT reinforced Thermoplastic Nanocomposites”, J. Compos. Mater., 52, 36813697 (2018) 10.1177/0021998318768390Search in Google Scholar

3 Dörner, J.Spritzgießen elektrisch leitfähiger Thermoplaste – Prozesstechnik und Modellbildung”, Diss., Universität Duisburg-Essen, Duisburg, Essen (2012)Search in Google Scholar

4 Dzulkipli, A. A., Azuddin, M., “Study of the Effects of Injection Molding Parameter on Weld Line Formation”, Procedia Engineering, 184, 663672 (2017) 10.1016/j.proeng.2017.04.135Search in Google Scholar

5 Holm, R., Holm, E.: Electric Contacts. Theory and Application. 4th Edition, compl. Rewritten, Springer, Berlin (1967, pr. 1979) 10.1007/978-3-662-06688-1Search in Google Scholar

6 Hopmann, C., Haase, S., “Prozessintegrierte Kontaktierung von elektrischen Funktionselementen mit elektrisch leitfähigen Kunststoffen”, Werkstoffe in der Fertigung, 52, 1820 (2015)Search in Google Scholar

7 Hopmann, C.Fragner, J. and Haase, S., “Direkte Kontaktierung durch Umspritzen”, Kunststoffe, 103, 178182 (2013)Search in Google Scholar

8 Kirkpatrick, S., “Percolation and Conduction”, Rev. Mod. Phys., 45, 574588 (1973) 10.1103/RevModPhys.45.574Search in Google Scholar

9 Kormakov, S., He, X.-X., Huang, Y., Liu, Y., Sun, J.-Y., Zheng, X.-T., Zheng, X.-T., Skopincev, I., Gao, X.-L. and Wu, D., “A Mathematical Model for Predicting Conductivity of Polymer Composites with a Forced Assembly Network Obtained by SCFNA Method”, Polym. Compos., 40, 18191827 (2019) 10.1002/pc.24942Search in Google Scholar

10 Li, Z. F., Luo, G. H., Zhou, W. P. and Wei, F., “Skin-Core Micro-Structure and Surface Orientation of Carbon Nanotube Composites by Injection Molding Process”, Solid State Phenomena, 136, 5156 (2008) 10.4028/ in Google Scholar

11 Papathanasiou, T. D.: “Flow-Induced Alignment in Composite Materials”, in Woodhead Publishing Series in Composites Science and Engineering, Guell, D. C: (Ed.), Woodhead Publishing, Sawston (1997) 10.1201/9781439822739Search in Google Scholar

12 Régnier, G., Dray, D., Jourdain, E., Le Roux, S. and Schmidt, F., “A Simplified Method to Determine the 3D Orientation of an Injection Molded Fiber-Filled Polymer”, Polym. Eng. Sci., 48, 21592168 (2008) 10.1002/pen.21161Search in Google Scholar

13 SadAbadi, H., Ghasemi, M., “Effects of Some Injection Molding Process Parameters on Fiber Orientation Tensor of Short Glass Fiber Polystyrene Composites (SGF/PS)”, J. Reinf. Plast. Compos., 26, 17291741 (2007) 10.1177/0731684407081352Search in Google Scholar

14 Schneidmadel, S., Koch, M. and Bruchmüller, M., “Effects of Fiber Orientation on the Electrical Conductivity of Filled Plastic Melt, AIP Conference Proceedings, 30007 (2016) 10.1063/1.4965477Search in Google Scholar

15 Shokri, P., Bhatnagar, N., “Effect of Melt and Mold Temperature on Fiber Orientation during Flow in Injection Molding of Reinforced Plastics”, Int. Polym. Proc., 21, 480486 (2006) 10.3139/217.0977Search in Google Scholar

16 Sun, X.-J., Lasecki, J., Zeng, D., Gan, Y., Su, X. and Tao, J., “Measurement and Quantitative Analysis of Fiber Orientation Distribution in Long Fiber Reinforced Part by Injection Molding”, Polym. Test., 42, 168174 (2015) 10.1016/j.polymertesting.2015.01.016Search in Google Scholar

17 Wabner, A.: “Beitrag zur Kurzschlussstrombegrenzung mit leitfähigen Polymercompounds in der Niederspannungsebene”, Diss., Technische Universität Chemnitz, Chemnitz (2001)Search in Google Scholar

18 Wegrzyn, M., Juan, S., Borrás, A. B. and Giménez, E., “The influence of injection molding parameters on electrical properties of PC/ABS-MWCNT nanocomposites”, J. Appl. Polym. Sci., 130, 21522158 (2013) 10.1002/app.39412Search in Google Scholar

19 Zallen, R.: The Physics of Amorphous Solids, Wiley-VCH, Weinheim (1998) 10.1002/9783527617968Search in Google Scholar

Received: 2019-08-22
Accepted: 2020-01-09
Published Online: 2020-04-09
Published in Print: 2020-04-29

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