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Efficient Application of Solder to Chip And Substrate Pads

IP.com Disclosure Number: IPCOM000100204D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 1 page(s) / 45K

Publishing Venue

IBM

Related People

Bertelsen, BI: AUTHOR

Abstract

This article describes techniques for selectively applying controlled amounts of molten metal alloys or mixtures to clean wettable pad areas. These molten alloys or mixtures, which are normally in the form of droplets, are charged and move under the influence of an applied electric field to the pads.

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Efficient Application of Solder to Chip And Substrate Pads

       This article describes techniques for selectively
applying controlled amounts of molten metal alloys or mixtures to
clean wettable pad areas.  These molten alloys or mixtures, which are
normally in the form of droplets, are charged and move under the
influence of an applied electric field to the pads.

      In one application of this principle, an ink jet nozzle is used
to form small charged droplets of predetermined size.  These droplets
are then transported under the influence of an electric field to the
pads at molten solder temperature.  By controlling the ultrasonic
pressure pulses, the charge on the droplets and the intensity of the
electric field used to move them from source nozzle to the pads, the
total volume of solder deposited on each pad can be controlled.

      Alternatively, the following technique can be used to deposit
charged droplets of solder on the pads.  It uses a thin sheet metal
that is wettable by solder and coated with a film of non-wettable
material on both sides and with holes etched through the sheet in the
pattern of pads on the wafer or module fingers.  The size of the
holes is selected to be slightly smaller than the pad size.  The
thickness of the sheet metal is selected to be such that, when a hole
is filled with solder, it will have enough to provide the needed
amount for a pad.  The sheet metal is dipped into molten solder which
causes a certain amount...