Fabrication method for gold bonding wire

A gold bonding wire fabrication method, which includes the steps of (a) drawing a non-gold wire rod, for example, a pure silver wire rod or pure palladium wire rod into a core wire of thickness within about 1 .mu.m.about.500 .mu.m, (b) electroplating the core wire with a layer of gold plating of thickness within about 0.025 .mu.m.about.25 .mu.m.

BACKGROUND OF THE INVENTION
 The present invention relates to a method of fabricating a gold bonding
 wire for use in IC, LED bonding, and more particularly to such a gold
 bonding wire fabrication method in which pure silver wire rod or pure
 palladium wire rod is drawn into a wire subject to the desired thickness,
 and then the pure silver wire or pure palladium wire is electroplated with
 a layer of pure gold coating. The invention relates also to a gold bonding
 wire made by this method.
 Regular gold bonding wires for IC bonding are directly drawn from a gold
 wire rod. Because these gold bonding wires are directly drawn from pure
 gold wire rod, their material cost is high.
 SUMMARY OF THE INVENTION
 It is main object of the present invention to provide a gold bonding wire
 fabrication method, which is practical for the fabrication of a
 high-quality, low-cost gold bonding wire. It is another object of the
 present invention to provide a gold bonding wire, which is inexpensive to
 manufacture. According to the present invention, pure silver or palladium
 wire rod is drawn into a core wire subject to the desired thickness, and
 the core wire is then electroplated with a layer of gold coating. After
 processed through an after treatment and a series of quality tests, a
 finished, low cost gold bonding wire is obtained.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 Referring to FIGS. 1 and 3, a non-gold wire rod 1 is processed through a
 wire drawing process 2 and drawn into a core wire 3 subject to the desired
 thickness. The core wire 3 is then electroplated 4 with a layer of gold
 coating 46, and then examined 5. When passed through the inspection, a
 finished gold bonding wire 6 is thus obtained.
 The aforesaid wire rod 1 is obtained from non-gold material in order to
 save material cost. According to tests, pure silver or pure palladium is
 the best choice for the non-gold wire rod 1, for the advantages of high
 signal conductivity and extendability.
 During the aforesaid wire drawing process 2, the wire rod 1 passes through
 the mold eye on at least one wire drawing die, and is drawn into the
 desired core wire 3 of thickness within 1 .mu.m.about.500 .mu.m. In order
 to improve the corrosion resisting power and signal transmission
 stability, the core wire 3 is electroplated 4 with a layer of gold coating
 46.
 Referring to FIG. 2 and FIG. 3 again, the electroplating process 4
 comprises in proper order, the step of degrease 41 where the core wire 3
 is washed with an alkaline solution, the step of rinse 42 where the
 degreased core wire 3 is rinsed with clean water, the step of acid active
 treatment 43 where the degreased core wire 3 is treated with an acid
 active surface treatment, the step of washing 44 where the degreased,
 acid-activated core wire 3 is washed with clean water, the step of gold
 plating 45 where the core wire 3 is covered with a layer of gold coating
 46, the step of washing 47 where the gold-plated core wire 3 is washed
 with water, the step of after treatment 48 where the surface of the gold
 coating 46 is smoothened, and the step of drying 49 where the gold plated
 core wire 3 is well dried. After drying, the electroplating process 4 is
 finished.
 After the electroplating process 4, the finished gold bonding wire is
 examined through a series of tests including signal transmission
 conductivity test, mechanical property test, wire diameter measurement,
 material analysis, and impurity content test. When passed, a qualified
 gold bonding wire 6 is obtained.
 As indicated above, the gold bonding wire 6 is comprised of a non-gold core
 wire 3, and a layer of gold coating 46 covered on the periphery of the
 non-gold core wire 3. Because the core wire 3 is drawn from pure silver or
 pure palladium, much material cost is saved.