Polyimide core bumps are formed by following steps: firstly,forming polyimide cores using photosensitive polyimide; next,metallization on the polyimide cores by sputtering; and finally,patterning the metallized layers. The polyimide core bumps thus preparedhave the advantages of larger aspect ratios, and better bump heightuniformity without conventional levelling process, and larger elasticitycompared with solid metal bumps such as gold or solder. Also variousbonding methods are applicable, such as soldering, or gold-tin bondingwith pressure and adhering, or other mechanical contact with adhesive
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