Laser Welding Accelerates for Automotive Electronic Enclosures

March 8, 2007

4 Min Read
Laser Welding Accelerates for Automotive Electronic Enclosures

European and Asian design engineers increasingly are turning to laser welding as a way to create box-like enclosures for electronic and other sensitive components used in cars, particularly under the hood. Financial, technical and legal issues had all stood in the way of laser fastening approaches for plastics such as PBT and nylon, but significant progress is now being reported.

“Laser welding is not here to rule out other types of welding processes” is the position of Jim Greene, vice president of sales and marketing for LPKF Laser & Electronics in Wilsonville, OR. “It doesn’t make sense to invest in laser welding if you can use a less expensive process like vibration or ultrasonic welding. What laser welding does is come in where the other types of welding processes leave off. For that reason, we see electronics as one of the main application areas.”

For new designs where electronic components may be subject to vibration or contamination, the more expensive laser welding is getting a close look.

One interesting example is a laser-welded tube used by Volkswagen in a dual clutch gearbox used in several models. Normally the part would have been made with the blow molding process. However, “this process would not have met requirements for a constant flow cross-section and even wall thickness,” says Michael Jacob, the design manager for IBS Filtran, the molder of the part. “There was also a danger of glass-fiber particles coming loose from the inner surface and damaging the delicate system of valves into which the tube carries the oil.”

“So we decided on injection-molding. For this we had to divide the tube into separate parts, to make demolding easier. However, we could not make two equal halves joined by conventional welding techniques, because the necessary contact surface area would have been too broad and welding-waste particles could have come loose; this had to be avoided.”

The designers decided on a tube that has open offset areas.

“One part made of a laser-absorbent variant of Zytel 70G30 HSLR can be molded in a tool with a single parting line,” Jacob continues. “Onto the open areas we then laser-weld two other injection-molded tops of the same nylon but using a laser-transparent variant. The weld-seam is very precisely defined and reliably air- and oil-tight. As the welding process does not involve oil-contact surfaces, there is no danger that particles of the plastic material come loose and enter the oil-stream. All in all, laser-transmission welding provides an optimum combination of cost-effectiveness and reliability.”

Laser welding works best from an economic perspective when it fits into an overall system, and is not viewed as a one-for-one replacement for ultrasonic or vibration welding, which is much less expensive from an equipment standpoint.

Laser welding economics also look best when a natural material can be teamed with a black, or other type, of laser-absorbing material. The issues become more complicated when designers require black-on-black. Special additives can make a very dark color laser-transmissive, but they are expensive. One of the companies that helped develop the technology also claims a patent on that approach. The patent has been upheld, and some automotive suppliers in Europe are now paying licensing fees.

Some design issues remain, however. “One challenge is that the industry does not have a measurement standard for transmissivity,” says Chul Lee, applications technology leader at BASF. Variables include the laser source, the wave length, part thicknesses, length of time the beam is exposed and how you clean the part surfaces. So far there is no ASTM or ISO test on transmissivity of specific resin grades under certain conditions. As a result, design engineers need to request samples that they can test under conditions that will be used in the production process. After the test, the design engineer, molder, equipment supplier and resin supplier need to agree on how quality will be measured at each stage of the process.

This laser-welded part carries oil from a filter to a gearbox on four different Volkswagen models.

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