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They are the unsung heroes of many technical products. Whether in the automotive sector, mechanical engineering, white goods, or tools, microswitches are essential for the safety and functionality of many products. However, without our adhesive sealants, they may not have been able to meet increasing automotive requirements.
Mechatronics company Marquardt is a leading manufacturer of microswitches and other electromechanical and electronic switches and switching systems. This independent family-owned company now employs more than 10,000 staff in 14 countries and achieves annual sales revenues of more than €1.3 billion. Since its foundation 1925, the company has been headquartered in the German town of Rietheim-Weilheim.
The 1045-Series is Marquardt’s signature switch. Millions of them are produced every year for the white goods and mechanical engineering sectors. This snap-action switch is designed as a push-button, switching a power circuit on and off by indirect actuation (NO/NC) or between two power circuits (changeover contact).
The sheer level of expertise applied to their manufacture is demonstrated by the fact that this switch, measuring just 5 mm x 20 mm x 20 mm and weighing only about 1 g, is designed for a mechanical service life of ten million switching cycles. Even still, after this time, the spring force still needs to function.
The head office of Marquardt in the German town of Rietheim-Weilheim (photo: Marquardt).
Until now, the extent to which adhesives in these switches have been used was for creating a durable bond between top and bottom switch components. However, increasingly stringent requirements in many sectors led Marquardt to make further use of adhesives' beneficial properties. Namely, switches now need to be reliably sealed from water and humidity in order for them to achieve IP 67 certification.
For this purpose, Marquardt’s switches must be hermetically sealed, including at their connection point. This can be achieved by applying a bead of adhesive around the circumference of the enclosure shell. The integrity of these seals depends upon their resistance to tearing or having any defective points. Furthermore, the pins that assure electrical contacts must be encapsulated. This means that no media must be able to penetrate the tiny gap between the pin and the injection-molded enclosure.
This calls for an adhesive that achieves good adhesion to enclosure shells made of glass fiber-reinforced polyamide as well as differently metallized pins. The resulting bond must also remain intact within the service temperature range of -40 to +100 °C. Given the required production volume, the adhesive must also cure in a matter of seconds to work in high-volume production settings.
Designed for ten million switching cycles: The microswitches in the 1045 series (photo: Marquardt).
Considering these factors, Marquardt chose a light-activated epoxy resin. Unlike more familiar light-curing products that are exposed to a light source after joining, this adhesive is designed for substrates that are impermeable to light. Irradiation takes place during preactivation, immediately after dispensing. Thanks to its chemical structure, it remains fluid for a short time—known as 'open time'—during which components can still be joined. This makes the process suitable for opaque materials such as the two enclosure shells of the switch. Afterwards, within just a few minutes and without further exposure to light, the adhesive achieves its functional strength.
After various strength and irradiation tests, Marquardt chose DELO KATIOBOND LA6078, a cationic adhesive developed by DELO Industrial Adhesives specifically for this application. It is applied to the underside of polyamide shells following plasma pretreatment, which increases their surface energy, making it easier to apply liquid adhesive. Next, a camera system detects the correct application of the fluorescent adhesive, after which the adhesive is quickly preactivated using a DELOLUX 80 LED lamp. The top shell is then joined and clicked into place before the switch is inverted for the next process, pin encapsulation. DELO KATIOBOND LA6078 is also used for this task, and it is then cured on a production line featuring five DELOLUX 202 LED area lamps. Here, too, the adhesive enables a production process lasting just a few seconds.
Particularly suitable for longer production lines: DELOLUX 202 LED area lamps.
To produce a reliable seal for microswitches, and to achieve IP67 certification, adhesives are paramount. In addition to their important contribution to the durability of components, they also ensure fast production processes with high yield rates.
Click below to learn more about the products used for Marquardt’s switches:
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