Browse Prior Art Database

Surface Mount Chip Packaging

IP.com Disclosure Number: IPCOM000060864D
Original Publication Date: 1986-May-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Curtis, SA: AUTHOR [+2]

Abstract

The presently available surface mount plastic leaded chip carrier (PLCC) is limited in the amount of heat it can dissipate, preventing some chips from using this package. The thermal enhancement described below would increase the thermal dissipation of today's PLCC and still maintain the leaded chip carrier's high reliability. The conventional PLCC package, shown in Fig. 1, consists of a chip 10 wire bonded to a metal lead frame 11. The chip and the bonded areas of the lead frame are then totally encapsulated in plastic material 13 and the leads are bent to complete the package. The improvement to this package, shown in Fig. 2, is to bond the lead frame 20 to ceramic 21 before plastic encapsulation. The ceramic becomes an outside surface of the package, thus allowing a much better thermal path to ambient air.

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Surface Mount Chip Packaging

The presently available surface mount plastic leaded chip carrier (PLCC) is limited in the amount of heat it can dissipate, preventing some chips from using this package. The thermal enhancement described below would increase the thermal dissipation of today's PLCC and still maintain the leaded chip carrier's high reliability. The conventional PLCC package, shown in Fig. 1, consists of a chip 10 wire bonded to a metal lead frame 11. The chip and the bonded areas of the lead frame are then totally encapsulated in plastic material 13 and the leads are bent to complete the package. The improvement to this package, shown in Fig. 2, is to bond the lead frame 20 to ceramic 21 before plastic encapsulation. The ceramic becomes an outside surface of the package, thus allowing a much better thermal path to ambient air. A heat sink that is thermal expansion matched to the ceramic (such as copper-molybdenum-copper or copper-INVAR*-copper) could be used to promote further heat dissipation. A low mass aluminum heat sink, which would not upset the thermal expansion system of the package, could also be used. Chips with C-4 bonds may also be adapted to this package by using tape automated bonding, as shown in Fig. 3. The addition of a ceramic interface from the chip to ambient air combined with the leaded surface mount package makes this application unique. Calculations show thermal resistance for a 44-lead PLCC would drop by a factor of 8. * Trademar...