Mitsubishi Engineering-Plastics Corp., Tokyo, says it has developed a superior compound for making three-dimensional antennas in cellphones.
The glass-reinforced alloy of polycarbonate and ABS contains as much as 30 parts per weight of a laser direct structuring (LDS) additive comprising antimony and tin.
LDS, developed by a German company called LPKF, has become an important approach to manufacturing molded-in cellphone antennas that conform to the shape of the part, allowing significant space savings. Addition of the metals that allow plating, however, has negatively impacted the mechanical properties of the molding.
The patent states: “As a result of intensive studies by the present inventors, it has been found that when the amount of glass filler is increased, although the mechanical properties are enhanced, the LDS activity is lowered.”
The Mitsubishi invention is an effort to overcome that problem. In one aspect of the invention, talc surface-treated with organopolysiloxanes is used to replace some of the glass fiber. In another aspect, some of the glass fiber is replaced with glass flake or a plate-like glass. Elastomers may be added to improve resistance to shattering. White pigment is also used in the compound for coloring.
Recycled polycarbonate can be used.
Mitsubishi is one of 19 materials companies that have developed proprietary compounds for the LDS process.