Fluent material handling – with receiver or receiver coacting mea – Filling or refilling of dispensers
Reexamination Certificate
1997-08-07
2001-02-13
Douglas, Steven O. (Department: 3751)
Fluent material handling, with receiver or receiver coacting mea
Filling or refilling of dispensers
C141S082000, C141S097000
Reexamination Certificate
active
06186192
ABSTRACT:
This invention relates to a jet soldering system and method.
Various soldering schemes have been developed for bonding semiconductor integrated circuit (IC) chips to a substrate (e.g., a printed circuit board). In some schemes, a semiconductor IC chip is bonded to a substrate by applying a small solder bump to the bottom surface of the chip, aligning the solder bump with a bond pad on the surface of the substrate, and heating the solder bump until it reflows. In some other schemes, solder bumps are applied to bonding pads on a substrate; afterwards, electronic components are bonded to the substrate by positioning the components over the solder bumps and by heating and reflowing the solder bumps. Some schemes bond IC chips to a patterned layer of solder created by applying a thin layer of solder paste to a substrate through holes in a stencil, leaving a selected solder pattern on the substrate. Recently, solder jet systems have been proposed for depositing solder droplets onto a substrate in a selected pattern. Such systems include a solder droplet ejector, which may eject solder droplets on-demand or continuously. In one proposed continuous solder jet system, a droplet generator vibrates to form a stream of solder droplets; an electrical charge is applied to the droplets and the charged droplets are passed between charged deflection plates which selectively direct the droplets to a target surface or to a catcher system.
SUMMARY OF THE INVENTION
In one aspect, the invention features, in general, an apparatus for filling filtered solder into replaceable solder cartridges for use in a system for depositing a selected pattern of solder onto a substrate on which electronic components are to be mounted. The apparatus includes a cartridge support, an environmentally-controlled chamber, a solder receptacle, a heater, a molten solder flow conduit, and a separator. The cartridge support bears the replaceable solder cartridge(s). The environmentally-controlled chamber receives the cartridge support and shields the interior of the chamber from external solder-oxidizing gases. The solder receptacle contains molten solder to be supplied to the environmentally-controlled chamber for filling solder cartridges therein. The heater heats solder contained inside the solder receptacle to a temperature at or above the melting temperature of solder to produce molten solder. The molten solder flow conduit is connected between the solder receptacle and the environmentally controlled chamber. The separator removes particulates and other debris from molten solder flowing therethrough prior to filling the solder cartridges.
Embodiments according to this aspect may include one or more of the following features. The solder receptacle includes an input for receiving pressurized gas for controlling the flow of molten solder from the receptacle. The environmentally-controlled chamber is a vacuum chamber capable of being pumped down to pressures between 10
−4
-10
−6
Torr or less. The solder filter includes porous material having pore sizes that are less than about 10 &mgr;m in diameter. The solder filter can be formed of sintered metal (e.g., stainless steel or other metal), sintered ceramic material, or ceramic foam. The cartridge support is rotatable about an axis. A cooler, adapted to receive a coolant for solidifying molten solder, is disposed around an output of the solder receptacle, thereby stopping the flow of molten solder through the output and into the solder cartridges.
In another aspect, the invention features a method for providing solder cartridges filled with solder. The method includes the steps of: supporting the replaceable solder cartridges inside an environmentally-controlled chamber protected from external solder-oxidizing gases; heating a supply of solder to a temperature at or above the melting temperature of solder to produce molten solder; filtering particulates and other debris from molten solder; filling molten solder into replaceable solder cartridges; and solidifying the solder in the replaceable solder cartridges.
Embodiments according to this aspect may include one or more of the following features. There are individual heaters that support respective cartridges. At the end of a filling operation, the molten solder is cooled at a location along the conduit upstream of a cartridge, to solidify the solder and thereby stop the flow of solder without the need for a valve. The filling of solder into the solder cartridges is controlled by applying a pressurized gas above molten solder produced by the heating step. The filtering step includes flowing molten solder through porous material having pore sizes that are less than about 10 &mgr;m in diameter. The filtering step includes flowing molten solder through sintered metal (e.g., stainless steel or other metal), sintered ceramic material, or ceramic foam. The environmentally-controlled chamber is evacuated to pressures of 10
−4
Torr or less. Nitrogen boiled off from a liquid nitrogen source is used after filling to bring the chamber up to atmospheric pressure and to cool the cartridges.
Embodiments may include one or more of the following advantages. The invention provides an efficient system for filling replaceable solder cartridges with filtered solder, reducing the likelihood of clogging the orifices of the solder cartridges. The cartridges are filled in an environment that reduces the likelihood of oxidation of the solder. Use of a cooler to solidify solder and thereby stop the filling of the solder cartridges eliminates the need for a solder flow valve, which may need frequent replacement due to the corrosive effects of molten solder and which may add to contamination.
Other features and advantages will become apparent from the following description and from the claims.
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Muntz Eric Phillip
Orme-Marmarelis Melissa E.
Pham-Van-Diep Gerald C.
Smith, Jr. Robert F.
Douglas Steven O.
Mintz Levin Cohn Ferris Glovsky and Popeo P.C.
Rapid Analysis and Development Company
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