Surface mount solder assembly of leadless integrated circuit pac

Details Surface mount solder assembly of leadless integrated circuit pac Surface mount solder assembly of leadless integrated circuit pac

1993-09-28

1994-09-13

Heinrich, Samuel M.

Metal fusion bonding

Process

Plural joints

2282481, 228254, 427191, 4273837, H05K 334

Patent

active

053461185

ABSTRACT:
Described are a process for soldering at least one component having solder bumps to a substrate and a process for forming solder bumps on metal pads of an element, such as an IC package or substrate or both. The bumps are formed by stencil printing solder paste deposits on the metal pads, heating the solder paste deposits to reflow temperature of the solder in the solder paste deposits, and allowing the molten solder in each deposit to coalesce and during subsequent cooling solidify forming the bumps on the metal pads. The bumps are formed by conducting the stencil printing through apertures in an ultra-thick stencil, the apertures having trapezoidal crossection in the plane normal to the broad surfaces of the stencil with the top opening being smaller than the bottom opening and with the walls of the aperture sloping at an angle within a range of from 1 to 45 degrees from the vertical, the solder paste having a low tackiness and high metal loading, and the solder paste deposits covering an area which is equal to or exceeds an area of the metal pad in any ratio between 1.5:1 and 5:1. Bumps formed in this manner lead to the formation of reliable solder joints.

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patent: 5211764 (1993-05-01), Degani
patent: 5261593 (1993-11-01), Casson et al.
IEEE Transactions on Components, Hybrids, and Manufacturing Technology, "Thermal Deformations Observed in Leadless Ceramic Chip Carriers Surface Mounted to Printed Wiring Boards," by Peter M. Hall, T. Dixon Dudderar and John F. Argyle, vol. CHMT-6, No. 4, Dec. 1983, pp. 544-552.
Microelectronics Package Handbook, Section 5-5, "Thermal Mismatch and Thermal Fatigue," by Van Nostrand Reinhold, 1989 edition, pp. 277-320.
Solder Paste Technology, by Colin C. Johnson and Joseph Kevra, Ph.D., TAB Books Inc., 1989, pp. 41-43.
BGAs Face Production Testing, by Dave Hattas, Advanced Packaging, Summer 1993, pp. 44-46.

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