Low exothermic thermosetting resin compositions useful as underfill sealants and having reworkability
View Patent ↗This invention relates to the thermosetting resin compositions useful for mounting onto a circuit board semiconductor devices, such as chip size or chip scale packages (“CSPs”), ball grid arrays (“BGAs”), land grid arrays (“LGAs”) and the like, each of which having a semiconductor chip, such as large scale integration (“LSI”), on a carrier substrate. Similarly, the compositions are useful for mounting onto circuit board semiconductor chips themselves. Reaction products of the compositions of this invention are controllably reworkable when subjected to appropriate conditions. And significantly, unlike many commercial rapid curing underfill sealants (“snap cure underfills”), the inventive compositions possess an exotherm under 300 J/g or demonstrate package stability at 55° C. for 7 days, and therefore do not require special packaging to be transported by air courier, or special approval from international transportation authorities, such as the U.S. Department of Transportation, to permit such air transport. The inventive compositions possess an exotherm under 300 J/g and/or demonstrate package stability at 55° C. for 7 days and therefore do not require special packaging to be transported by air courier, or special approval from international transportation authorities, such as the U.S. Department of Transportation, to permit such air transport.
1. A method of providing an underfill sealant between a semiconductor device or a semiconductor chip and a circuit board to which said semiconductor device or said semiconductor chip is electrically connected, and subsequently reacting said underfill sealant, reworking said underfill sealant, and removing said semiconductor device or said semiconductor chip from said circuit board after said semiconductor device or said semiconductor chip has failed, the steps of which comprise:
(a) dispensing said underfill sealant between said semiconductor device or said semiconductor chip and said circuit board;
(b) exposing said underfill sealant, as so dispensed, to a temperature of from about 80° C. to about 150° C. for a period of time of from about 5 minutes to about 60 minutes to cause said underfill sealant to form a reaction product;
(c) discovering a failure with said semiconductor device or said semiconductor chip;
(d) softening said reaction product by heating at a temperature of from about 190° C. to about 290° C. for a period of time of from about 10 seconds to about 60 seconds; and
(e) removing said semiconductor device or said semiconductor chip from said circuit board by inserting a metal piece between said semiconductor device or said semiconductor chip and said circuit board while said reaction product is soft and lifting said semiconductor device or said semiconductor chip from said circuit board;
wherein said semiconductor device includes a semiconductor chip mounted on a carrier substrate;
wherein said underfill sealant, as so dispensed, is thermosetting resin composition comprising:
(1) an epoxy resin component comprising a combination of a first bisphenol epoxy resin, a second bisphenol epoxy resin different from said first bisphenol epoxy resin, and a cycloaliphatic epoxy resin;
(2) an inorganic filler component having a mean particle size distribution of about 1 to about 1,000 nm; and
(3) a thermal initiator capable of liberating a cationic catalyst; and
wherein said thermosetting resin composition exhibits an exotherm of less than 300 J/g when exposed to a temperature of from about 80° C. to about 150° C. for a period of time of from about 5 minutes to about 60 minutes.