Flexible circuit substrate

#1. Field of the Invention

#The invention relates to a flexible circuit substrate, more particularly to a flexible circuit substrate having an improved peel strength.

#2. Description of the Related Art

#Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments with reference to the accompanying drawings, of which:

#FIG. 1 is a sectional view of a conventional flexible circuit substrate;

#FIG. 2 is a sectional view of the first preferred embodiment of the flexible circuit substrate according to this invention;

#Referring to FIG. 2, the first preferred embodiment of the flexible circuit substrate according to this invention is shown to include a polyimide film 21, a chromium layer 22 sputtered on the polyimide film 21, a nickel-chromium alloy layer 23 sputtered on the chromium layer 22, a first copper layer 24 sputtered on the nickel-chromium alloy layer 23, and a second copper layer 25 plated on the first copper layer 24.

#Referring to FIG. 3 and Table 1, the process for manufacturing the first preferred embodiment of FIG. 2 includes the following steps:

#(1) The chromium layer 22 is sputtered on the polyimide film 21. The polyimide film 21 is a square film that is 10 cm×10 cm in size. The chromium material for the sputtering step is a square material that is 20 cm×20 cm in size. The sputtering is performed for 1 minute in an argon atmosphere. The electric current applied during the sputtering step is 1.0 A. The pressure of the sputtering gas is 5×10−3 torr. The flow of the sputtering gas is 2×10−3 torr. The distance between the polyimide film 21 and the chromium material for the sputtering step is 20 cm. The thus-formed chromium layer 22 has a thickness smaller than 1 μm.