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From cooling off in the summer heat to dehumidifying the autumn rain, to keeping you warm in the wintertime, in-car climate control systems are an essential commodity. Fan motors are an integral component to their operation, with thermally conductive adhesives making an important contribution to their assembly and operation.
Now-defunct Sitronic was one of the automotive industry’s leading suppliers of automotive electronic components such as blower controllers. During their time in business, they worked with OEMs such as Volkswagen, BMW, and General Motors, as well as agricultural machinery manufacturer Claas.
To perform as desired, climate switches must operate at a high current. Sitronic offered various performance classes with load currents between 18 A and 35 A, with voltages of either 12 V for passenger cars or 24 V for commercial vehicles. Space behind the dashboard is scarce, so these systems rely on compact heat sinks. With such heat accumulating in such a small space, a thermally optimized design is also crucial.
Optimal heat dissipation can be achieved through thermally conductive bonding between the printed circuit board and the heat sink. Sitronic at the time searched for an adhesive with particularly good thermal conductivity. Resistance to peak temperatures of up to 160 °C and good adhesion to copper inlays found in PCBs as well as to the die-cast aluminum heat sink were additional requirements. The adhesive would be tasked with joining the heat sink and the housing made of high-performance PA66 GF30 plastic material.
The following tests were conducted:
Blower controllers for air conditioning systems: The more compact the design, the better the heat dissipation must be (Figure: Sitronic).
Following these three suitability tests with different products, Sitronic opted for a thermally conductive DELO MONOPOX epoxy resin from DELO Industrial Adhesives. This is a robust adhesive, specially designed with more fillers for increased thermal conductivity to meet Sitronic's specific needs. In addition, it provides considerable benefits for efficient processing.
Among them is easy processing as a one-component product, since mixing systems are not required and mixing errors are thus avoided. The adhesive is silicone-free, a characteristic generally desired by the automotive industry due to the risk of outgassing in downstream processes. Furthermore, the product cures in one process step—as quickly as 40 minutes at 150 °C—and can be used for both bonding tasks thanks to its universal adhesion. This simplifies production as only one dispensing system is needed, used for bonding the heat sink to both the PCB and the housing.
Blower controller production starts off with components being subjected to atmospheric pressure plasma pretreatment. This increases component surface energy and improves the adhesive's effectiveness. Immediately afterwards, the adhesive is dispensed through an eccentric screw valve. The components are joined before the adhesive finally cures in an air convection oven.
The tunnel oven used ensures high throughput and efficient production. Sitronic was thus able to achieve the high volumes required to serve the numerous OEMs and tier-1 suppliers.
Are you looking for a similar adhesive for your project? Check out our Customer Innovation Center to see how we can work with you to fill your needs!
DELO is a leading provider of high-tech adhesives. For over 25 years, we have offered solutions for the automotive, electronics, and semiconductor industries. Our innovative technologies set industry standards. Companies like Bosch, Huawei, and Siemens rely on DELO for superior adhesive technologies.
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