Applicable Business AreasAutomotive manufacturers, industrial equipment manufacturers, consumer equipment manufacturers, residential equipment manufacturers, and Tier 1 suppliers of each manufacturer
Target ApplicationsAutomotive, industrial equipment, consumer equipment, and residential equipment
Insert molding, in which a metal component is inserted into a mold and plastic is injected to form an integrated component, enables the combination of the characteristics of each material, such as the electrical conductivity and heat dissipation of metals and the moldability and lightweight properties of plastic. However, adhesion at the plastic-metal interface is not sufficient, and there are challenges in ensuring airtightness to prevent the ingress or leakage of gases and liquids.
As a method to ensure airtightness, sealing by potting adhesive at the plastic-metal interface is widely known; however, this method requires surface modification and heating processes before and after the potting process, and there remains an issue in that the molded product becomes larger due to the space required for the adhesive. In addition, a physical sealing method using gaskets and bolt fastening can achieve a high level of airtightness, but it inevitably increases the number of components and processes.
To address these issues, Resonac improves airtightness in insert molding through laser-based plastic-metal bonding technology. Compared with conventional methods, including bolt fastening, process reduction is possible, and miniaturization of molded products can be achieved.
Figure 1. Comparison of sealing methods for plastic-metal composite products
In our plastic-metal bonding technology, a metal component with a laser-roughened surface is inserted into a mold, and plastic is injected to form a strong bond. Table 1 shows the results of helium (He) leak tests and failure modes for various combinations of metals and plastics. High airtightness was confirmed for all combinations. In addition, the failure mode was fracture of the plastic base material, indicating that the plastic-metal bond is strong.
Since the plastic-metal interface is directly bonded, miniaturization is possible compared with molded products obtained by conventional methods using adhesives. Furthermore, the high degree of design flexibility allows us to propose molded products that can be integrated even when there are constraints in space or shape.
Table 1. Results of He leak tests and failure modes of plastic-metal bonding
This plastic-metal bonding technology can be applied to both shaft seals and face seals.
A three-phase terminal block is a component that connects an inverter and a motor in automobiles, and with increasing motor output and torque, the temperature of the busbar during operation tends to rise. In response to this trend, we propose a three-phase terminal block capable of ensuring reliability under higher-temperature environments. Since there is no need to use adhesive, processes such as electrode surface modification, adhesive potting, and heat treatment can be eliminated, enabling the miniaturization of molded products.
Figure 2. Application example of a three-phase terminal block
Figure 3. Process of shaft sealing
By switching from gasket and bolt fastening to sealing by plastic-metal bonding for a composite product consisting of a heat sink and a plastic housing, it is possible to simultaneously reduce the number of components and processes.
For the plastic cooler joined by plastic-metal bonding, various reliability tests including high-temperature environments were conducted, and it was confirmed that airtightness was maintained under all test conditions (Table 2).
Figure 4. Process of face sealing
Table 2. Example of reliability evaluation results for a plastic cooler3)
Published: August 6, 2026
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