SMT & Inspection | June 12, 2006
Macromelt® Provides Solution for Auto Safety System
Fueled by technology development and increased device functionality, significant advances in automotive technology are occurring at a rapid pace. Over the last several years, automotive electronics has experienced dramatic growth - between 10% and 15% per year. And, with advances in automotive safety and comfort devices, the total electronics content of modern vehicles will only continue its upward climb.
By: Michael Pierce, the electronics group of Henkel and Matt Slaughter, D&R Technology, LLC One area that has seen dramatic improvement is passenger safety. Since the introduction of the first airbag system several years ago, the feature content, reliability and performance of passive restraint systems have been continually improved, resulting in significant injury and fatality reductions. Driven by the Federal Standard FMVSS 208 for Occupant Crash Protection, smart air bag systems are now a requirement for all vehicles produced in 2006 and beyond. These air bag systems can detect the presence and discern the size of the vehicle occupant and deploy multi-stage airbags that reduce the likelihood of occupant injury. A key component of smart air bag systems is a belt tension sensor (BTS) device that informs the safety controller system of seat belt tension during normal use. Manufactured by D&R Technology, LLC, the sensor incorporates a printed circuit board with miniaturized surface-mount components, a coated steel structural bracket and plastic housings. Though D&R considered using traditional potting compounds and epoxies for protection of the sensor electronics, these options did not provide sufficient process speeds or device insulation. Henkel's Macromelt® material, however delivered the solution D&R was looking for. Through collaboration with a Tier 1 automotive supplier and thanks to Macromelt's unique process capability and cure speeds, D&R Technology was able to introduce a robust new product to meet the Federal requirements three years ahead of the 2006 deadline - a timeline that is almost unheard of! This accelerated design, validation and technology introduction was, in part, made possible by the use of Henkel's patented Macromelt product, an innovative material that speeds the encapsulation process on the order of ten times faster than that of traditional potting or injection molding systems. Macromelt is a low pressure molding solution that replaces traditional injection molding or potting. The polyamide hotmelt provides a fast and convenient packaging solution that both encapsulates the circuitry and forms the outer shell of the device, delivering a self-contained, integrated assembly. Use of Macromelt also dramatically reduces the number of process steps required by conventional potting and reduces the manufacturing time, cost and complexity of the encapsulation process. Macromelt's low viscosity is key to the success of the molding process. With an application pressure of between 20 to 500psi, the low pressure in the mold cavity does not risk damaging the sensitive electronic surface mount components. The hotmelt polyamide adhesive is able to flow around the tightest dimensions without the high levels of pressure required by traditional materials, significantly reducing stress even for highly miniaturized components. The material's cure speed is exponentially faster than that of potting materials - a characteristic which was a critical factor in D&R's choice of Macromelt technology, as the company is producing millions of sensors per year. Plus, Macromelt not only delivers the cycle time performance the leading automotive manufacturer requires, but a robust package as well. In D&R's view, there are several benefits to this unique material, the most important of which is the overall value to the customer, both from a process/performance perspective as well as from a customer support perspective. Other key advantages are the robust structural properties that enabled the incorporation of a strain relief detail in the sensor, the excellent adhesive properties that allow superior bonding to all of the electronic materials, the incredibly short cycle time and the delivery of a highly repeatable process. In a nutshell, Macromelt had everything that D&R needed to develop, validate and introduce a new product three years ahead of the Federal requirement, enabling the production of safer vehicles for all motorists.