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Partnering May, 2019
Thermally Conductive Adhesive for Air Conditioning Power
Electronics Keeps the Air Flowing By Alexander Wörner, Head of Sales, DELO A
ir conditioning systems are re- quired to cool off hot cars with- in a short period of time during
the summer months, to dehumidify the air in the autumn rain and to provide heat within a few minutes during the winter. Each of these functions means heavy work for the blower controllers of the fan motors installed in the air duct or in the motor mount of an automobile. Al- though they are not visible, thermal- ly conductive adhesives offer an im- portant contribution to making this process work. Sitronic, a supplier of power
electronic components, manufac- tures blower controllers used in ve- hicles. In addition to the controllers, the automotive electronics specialist also produces control and operating systems, lighting technology, and sensors, like dew point and wind- shield temperature sensors to pre- vent fogging. From its development and pro-
duction sites in Germany and its rep- resentative offices in the U.S., South Korea and China, the family-owned company not only provides products
to Tier 1 suppliers, such as Denso and Valeo, but also to OEMs that in- clude General Motors, Volkswagen and BMW.
Small Heat Sinks To ensure they deliver the re-
quired performance, a great deal of current must flow through the blow- er controllers, which are partly fitted without screws. The company offers various performance classes with load currents between 18 and 35A. The voltage is either 12V for passen- ger cars or 24V for commercial vehi- cles. Since space in cars is scarce, Sitronic relies on compact heat sinks. Given the heat accumulation in a small space, a thermally optimized design is crucial. An optimized heat dissipation
can be achieved through thermally conductive bonding between the print- ed circuit board and the heat sink. Be- cause these various requirements needed to be met, Sitronic had been looking for an adhesive with particu- larly good thermal conductivity, resist- ance to peak temperatures of up to 320°F (160°C), as well as good adhe-
sion to the copper inlays of the PCB and to the die cast aluminum heat sink. In addition to all of the core re- quirements, the adhesive also had to be suitable for joining the heat sink and the housing made of high-per- formance PA66 GF30 plastic material. The specified adhesive proper-
ties, including thermal conductivity, temperature resistance, and adhesion, were tested in a thermal cycling test with 12,000 cycles and temperatures varying from –22 to +257°F (–30 to +125°C), a shaker test and a final func- tion test regarding heat dissipation.
Benefits in Processing Following these three suitabili-
ty tests with different products, Sitronic opted for the thermally con- ductive DELO MONOPOX AD292 epoxy resin from DELO Industrial Adhesives. This robust adhesive is specially designed with more fillers for increased thermal conductivity, meeting Sitronic’s specific needs. In addition, it provides considerable benefits for efficient processing. The adhesive can be processed easily as a one-component product,
because mixing systems are not re- quired. It is also silicone-free, a prop- erty generally desired by the automo- tive industry that eliminates the risk of outgassing in downstream process- es. The product is able to cure in one process step — for example within 40 minutes at 302°F (150°C) — and can be used for both bonds, due to its uni- versal adhesion. This simplifies plant construction, since only one dispensing system is needed, which can be used for bonding the heat sink to both the PCB and the housing.
DELO MONOPOX AD292
requires no mixing system and is silicone-free, elimi- nating the risk of out- gassing during down- stream production.
Sitronic starts its blower con-
troller production by subjecting the components to atmospheric pressure plasma pre-treatment. This increases the surface energy of the components and improves adhesion. Immediately afterwards, the adhesive is dispensed through an eccentric screw valve. The components are joined before the ad- hesive is finally heat-cured. The air convection tunnel oven
SCS PRECISIONCOAT V
used to cure the adhesive ensures high throughput and efficient pro- duction. Because of this, Sitronic can achieve the high volumes required to serve the numerous OEMs and Tier 1
suppliers it works with. Contact: DELO Industrial
Adhesives, LLC, 144 North Road, Suite 2650, Sudbury, MA 01776 % 978-254-5275 Web:
www.delo-adhesives.com/us r
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