PHOTORESIST WITH ANTI-CRACKED AND FINE PROFILE FOR HIGH-SPEED GOLD BUMP PLATING

The anti-cracking and the profile of thick layer positive photoresist, for high speed gold bump plating in the surface mounting technology, has been improved by selection of molecular weight of novolack resin a nd developing method. The conventional resist pattern lines were crack ed frequently at the plating temperature under 60 degrees C, on the ot her hand, these new resin with higher molecular weight resin were prot ected from being cracked and hold fine profiles at 70 degrees C. Frequ ent replacement of developer during puddle development shorten the dev eloping time to 70% and made fine pattern profile with straight vertic al side walls. With this improvement, the square gold bumps 20 x 20 mu m with 20 mu m in thickness has been sufficiently formed in the halft ime of the conventional process.