Browse Prior Art Database

Discrete Solder Apply Technique Utilizing Incompressible Working Fluid

IP.com Disclosure Number: IPCOM000120643D
Original Publication Date: 1991-May-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 4 page(s) / 129K

Publishing Venue

IBM

Related People

Tangirala, US: AUTHOR [+3]

Abstract

Disclosed is a technique for simultaneous application of discrete, uniform, and controlled amounts of solder. This invention utilizes an incompressible fluid and piston cylinder system to manipulate the solder. Henceforth, the term "solder" shall apply to low temperature eutectic solder, tin/lead alloys, and other low liquidus point metal soldering systems.

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This is the abbreviated version, containing approximately 52% of the total text.

Discrete Solder Apply Technique Utilizing Incompressible Working Fluid

      Disclosed is a technique for simultaneous application of
discrete, uniform, and controlled amounts of solder.  This invention
utilizes an incompressible fluid and piston cylinder system to
manipulate the solder.  Henceforth, the term "solder" shall apply to
low temperature eutectic solder, tin/lead alloys, and other low
liquidus point metal soldering systems.

      A typical embodiment is the application of solder onto several
pads on a carrier surface prior to the placement of components.  This
is of prime concern in chip-on-board bonding, where pad dimensions,
density and spacings preclude the use of many conventional methods,
such as solder screening and solder levelling, as discussed in the
prior art section.  This technique is also applicable to fine pitch
surface mount and tape automated bonding processes.

      The tool consists of three basic parts: a faceplate, a chamber,
and a piston.  Each of these parts could be made of one single
material or a combination of any materials which have low surface
energies and do not stick to molten solder. Examples include
aluminum, stainless steel, titanium, or an engineering plastic, such
as high temperature polyimide.

      The faceplate has cylindrical through holes matching the pad
pattern on the carrier.  If the physical limits are reached for
effectively creating the holes on the faceplate, fewer holes can be
created on the faceplate and the tool can be operated in step and
repeat mode to cover the entire pattern of a chip site on a carrier.

      The chamber and the piston can be one single unit.  The chamber
is filled with an incompressible fluid, such as Fluorinert*,
solder-pot oils, or other high-temperature, non-volatile inert
fluids.

      This tool can be operated in two modes: "the solder pick-up
mode", and "the solder-in-chamber mode".  In the "solder pick-up
mode", the solder is picked up from an external solder source and
released so that uniform amounts of solder fall precisely on to the
designated spots on the carrier.  In the "solder-in-chamber mode"
solder is be stored inside the tool in a molten state and precise
amounts dispensed through several holes simultaneously.

      The tool does not have to be but may be mounted on the end
of the arm of a robot for high throughput operation. The tool head
may or may...