Sensors and control units

Joining a radome to the radar housing using the heat staking processes BHS HOT STAMP®

For the joining of a radome to the radar housing, a customer opted for heat staking processes instead of an originally envisaged bolting process in order to meet today's requirements for technical cleanliness and to save running costs. In designing the riveted joint, the customer followed the bdtronic design guideline. 

The heat staking as the last manufacturing step is carried out via four riveting points in the product corners, whereby the free area around the riveting points for forming the rivet heads and supporting the tools is very tight. Joining of the radome to the housing as a "sandwich" structure takes place after metering of the liquid seal, which may be exposed to a maximum temperature of 80°C during the curing time of approx. 24 hours. 

The BHS HOT STAMP® heat staking processes were chosen because they generate a very low temperature input on the component and the tools have the smallest diameters. The process simulation in the in-house technology center with subsequent service life tests in accordance with relevant standards by the customer showed that all requirements were met. The pin material selected is a special, durable semi-crystalline thermoplastic. 

In the production flow, the assembly was transported into the hot riveting machine in such a way that the riveting pins were on the underside of the assembly, so that riveting against the direction of gravity was desired in order to dispense with turning the assembly before riveting. Turning the assembly after dispensing the sealant and bringing the entire assembly together is risky, as doing so could possibly negatively affect the cross-linking and bonding of the sealant. 

BHS HOT STAMP® enables this process direction, which reduces the investment costs of the machine and allows the production sequence to be reproduced safely. A special punch was designed for the series production line which can be guided through the hold-down mask. Diverse product variants, some with different material types, are produced in a large number of production lines worldwide with a cycle time of 15 seconds.

Joining of a wheel housing using the heat staking process BHS HOT AIR®

For other radar systems, hot-air riveting is used to join and securely position antennas to radomes, printed circuit boards to housings, plastic-plastic pairings, or cooling plates in housings. The BHS HOT AIR® heat staking processes ensure maximum holding force and secure gap filling to achieve motion-free positioning. The hot riveting machine for joining two plastic parts made of different thermoplastic materials has to work in cycle with 4-cavity injection molding machines and rivets a component every three seconds.

Control units

A classic and state-of-the-art hot riveting application is the joining of a printed circuit board to a plastic carrier, whether housing, side panel or carrier plate. Hot riveting has long since replaced alternative joining methods such as screws. This is partly for cost reasons and partly because of the high demands on technical cleanliness in automotive electronics. 

In the present application, connector sockets are caulked to the printed circuit board, where the rivet points must withstand forces of at least 300N during installation. Due to the subsequent installation situation in the vehicle, the rivet head height is limited. There must be no bubbling, residual dirt or melt leakage. The riveted assembly then undergoes a reflow soldering process at > 270°C. The heat stamp process is used here. 

The BHS HOT STAMP® heating stamp process is used here, which has won out over alternative technologies such as ultrasonic, infrared, simple hot stamp, laser or hot air processes. Depending on the production site, the machines are designed for manual loading and unloading or for inline solutions.