This paper discrusses the resauS of CrOIIIparative reldnlity testing of electronic Multichip M d e s (MCMs) fabricated with laminate substrates (MCM-L) and protected with various bare-die coatingsTIre demonstration MCMs incflip-chip and wire-band design versions of the digital portim of a Global Positioning System ( G P S ) Receiver MCM and an analog MCM for use in general aviation a p p l i d m . Standard encapsulants and new inorganic coatings, D mComing's ChrpSeaP h e d c coatirg " a h 7 -evaluated using e " r i d stress exposures far high reliabdity avioIlic;s appIic&m. FnlI wafa-pmtre testing was performed before and after the slqspk" chipseal@ processing and @hip wafer bump processing s t e p . and fhp-~h~p w a k r processing steps were shown to cause no device yield do n on the five different semiconductor wafer lots tested. Environmental test results demonstrated that designed for very robust, high reliability applications such as miti.tary and commercial avionics. low cost MCM-L Units with bare die packaging cm be INTRoDucTLBN For many years high reliability applic;Ztiom haxe requirecl W c packaging approaches to protect delicate integrated cirudts (ICs) from damage. These applications involve some combination of harsh enviromnents, long &rage life, long operating life, of sitnations where hsxman lives or mission success depend Specialized hermetic IC packages performed well in these applications but &ed with them a number of size, weight, speed, and cost penalties. Mu& has been written about the recent improvements made in conventional plastic packagmg approaches, and sigmficant advancements have been made in plastic molding and encapsulation materids and pcesses. Improved expansion ChWristics, &tic moduhq adhesion, and p&cation levels have signigcantly upon the robustness of the electronic pihckaging. 0-7803-4449-9/98/$10.00 1998 IEEE i".sed the robustrress of p h t i c molded a d encapsalated ICs. In soape cases, phtic packages axe now "good e"gW to be used in applications which previously required h&c packaging. However, it is i9lpartan;t to keep i n mind that most plastic packaged ICs have been devehped fox high volume, cost-se~+itive t y p a l life cycles of a few years, or even month, so that Iong tam r&&iIity is not USE& a major c o " dnring design and "ukEBbm to assess &e have s-parkd many debates over tfre validity of various test m e & & Cansnmerpr0dudm;mrrf;rc~aretypically satisfied if their devices pass h & humi* (85°C/850/aRH) anrd autoclave ( 121°C/99.6a/QRH) exposures.relrabtlitp "ers usuaUy demand more &ceming Highly Accekmkd Stress Test (HAST) methods ( 1 4 0 n C / 8 P / a e bias). In the more severe HAST eq"es, pIastic pacEraged ICs w i l l last from less than a hundred burs to sevezal lmndred h o m dependhxg on the "diictwer and @ty of the part. On the other h d , property fabricated hermetic package ICs wiIl m i v e over 1000 hours of HAST with less than a five percent fBi1m-e rate, defined in this paper as hermetic-equivalent perfmname [ 11.All packages for ICs introduce the penalti...
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