Semiconductor package lead plating method and apparatus

Details Semiconductor package lead plating method and apparatus Semiconductor package lead plating method and apparatus

1999-10-13

2001-11-13

Dunn, Tom (Department: 1725)

Metal fusion bonding

Process

Plural joints

C228S254000, C228S042000, C228S043000, C228S206000, C029S743000

Reexamination Certificate

active

06315189

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to semiconductor device packages, and more particularly to a method and apparatus of plating package leads which cannot be immersed in liquid solutions.
BACKGROUND OF THE INVENTION
The leads of semiconductor packages are often solder plated after the package is formed. Many packages are moisture sensitive and cannot be placed in solder flux or other solutions which may be used in the plating process. A wave soldering process is often used in plating leads by moving the device leads across the top of a solder source to coat the leads with solder. This can cause buildup of solder on the leads and also forms solder bridges between the leads.
The use of a soldering bath is described in U.S. Pat. No. 5,161,727. A non-oxidizing atmosphere is used above a solder bath and a conveyor is used to move the parts to be solder plated over the solder bath. This patent defines in particular the housing for providing the non-oxidizing atmosphere above the solder bath.
An apparatus for circulating hot air and a method for wave soldering is defined in U.S. Pat. No. 5,379,943. A fluxed is used to apply the flux to the item to be soldered. High pressure air is circulated within the apparatus and directed against the fluxed surfaces prior to the application of solder.
Additional solder apparatus are described in U.S. Pat. Nos. 5,240,169, 5,228,614 and 5,722,581.
SUMMARY OF THE INVENTION
The invention is a method and apparatus for solder plating leads on semiconductor packages. In the method for solder plating the leads of a semiconductor device, an apparatus in a controlled atmosphere picks up a semiconductor in a carrier. The carrier is moved through a preheat and clean station where a reducing gas cleans the leads. The semiconductor package leads are then moved into a solder bath where the leads are contacted with molten solder, or coated with a solder paste. Partially through the bath, the package is rotated ninety degrees to allow solder to flow along the lengths of the leads originally extending transverse to the movement of the package leads through the solder. The package leads are removed from the solder and a gas, for example N
2
, is blown across the leads to level the solder on the leads, and to remove solder bridging the leads. The package is then moved to an unload station.
The apparatus used in he plating process includes a continuous conveyor track on which is mounted at least one carrier apparatus which is used to carry a package through the plating process. The carrier has a plurality of flexible legs that are sprung open at a pickup station to received a package. A vacuum may be used to draw the package upward between the flexible legs. The vacuum holds the package in place until the carrier begins to move and the flexible legs are allowed to move toward the package, holding it in place. The carrier has a gear to which the flexible legs are attached to permit the flexible legs and package to be rotated when over the solder plating bath to allow uniform flow of solder during the plating process.


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IBM Technical Business Disclosure, Nov. 1988, TBD-ACC-NO: NN8811367, vol. 31, Issue 6, pp. 367-369, Nov. 1988.

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