ABSTRACT
The conventional pretreatment of polymers for the metallization by electroplating is based on hazardous and polluting agents like chromic acid and various organic solvents. We report on the metallization of glass fiber reinforced poly(butylene terephthalate) (PBT 20% glass fiber, CRASTIN SK 603® by DuPont) by electroplating without using such chemicals as pretreatment agents. This chemical step is substituted by a low pressure plasma pretreatment of the polymer surface.
The plasma pretreatment of CRASTIN SK 603 was performed in a parallel plate reactor operating at 13.56 MHz. Oxygen or argon/oxygen mixture were used as plasma gases. A plasma pretreatment time of 5-10 minutes leads to an excellent adhesion strength up to 2 N/mm as measured by a 90° peel test on the electroplated metal coatings. Both the roughening as well as the activation of the polymer surface are essential for good adhesion. The pretreatment time of more than 10 minutes leads to lower adhesion strength.
A combination of a selective plasma activation through a metal mask followed by a maskless Pd-seeding process leads to the deposition of patterned metal lines on the polymer. Thus, this is a promising method for the direct deposition of conductor lines by electroplating as needed for the 3D moulded interconnect devices (3D-MID). 100 μm wide conductor lines were deposited by this metallization process (even areas at an angle of 90° to the base plate were metallized). Thus, a combination of a low pressure plasma pretreatment and electroplating takes advantage of the specific merits of both processes. The plasma activation of polymers replaces hazardous and polluting chemicals insuring a safe and fast pretreatment whereas electroplating offers an economically attractive metallization of polymers.
