Metal fusion bonding – Including means to apply flux or filler to work or applicator
Reexamination Certificate
1996-09-23
2001-08-21
Heinrich, Samuel M. (Department: 1722)
Metal fusion bonding
Including means to apply flux or filler to work or applicator
C228S254000, C228S262000, C239S102200, C239S600000, C222S593000, C118S300000
Reexamination Certificate
active
06276589
ABSTRACT:
BACKGROUND
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
The invention features, in general, an apparatus for depositing a selected pattern of solder onto a substrate comprising a substrate support, a solder ejector, and an orifice-defining structure. The substrate support has structure for bearing a substrate on which one or more electronic components are to be mounted. The solder ejector has a cavity-defining structure that defines a cavity for containing molten solder. The orifice-defining structure is a flat disk that has an orifice therethrough for producing a stream of molten solder. The disk is supported around the orifice on a disk supporting structure that is replaceably coupled to the cavity-defining structure.
Embodiments of the invention may include one or more of the following features. The orifice preferably has a characteristic length (L) along a length dimension through the orifice-defining structure and further has a characteristic diameter (D) in a plane transverse to the length dimension, the ratio L/D being less than or equal to unity. The ratio L/D is preferably at most equal to 0.25. The flat disk that defines the orifice is supported on a base underneath a cap having a cap orifice that is larger than the orifice of the disk. The base and the cap have respective mating threads. The base defines an annular lip around the seat for receiving an o-ring that is in a compressed, fluid-tight state when the disk is pressed against the seat. The base is threadedly connected to the cavity defining structure, and an o-ring is compressed when there is rigid connection between the base and the structure. There can be apertured plates on both sides of the flat disk that support the disk around the orifice but do not interfere with flow to the orifice-defining disk and the stream of ejected solder. Preferably the cavity defining structure is a replaceable solder-containing cartridge, and the base is sealably and rigidly connected to it. The disk is non-wettable by molten solder. The apparatus includes a vibrator to cause droplets to form from the molten solder stream in a desired frequency.
Instead of a cylindrical orifice through the disk, the disk can have a hemispherical or conical cavity leading to a cylindrical orifice.
Embodiments of the invention may include one or more of the following advantages. The solder deposition system can be easily cleaned and maintained, while depositing solder onto a substrate in a highly uniform, repeatable and predictable way. The orifice structure can be replaced while reusing the remaining components. The use of orifices with the specified L/D ratios provides uniformity and the repeatability of the deposited droplets. The rigid, metal-to-metal sealing of the base with the replaceable, orifice-defining disk, and the rigid, metal-to-metal engagement of the base with the replaceable cartridge reduces problems caused by harmonic and sub-harmonic vibrations between the disk and the base and between the base and the cartridge, which would otherwise affect the uniformity of the deposited droplets.
In another aspect, the invention features, in general, an apparatus that deposits a selected pattern of solder onto a substrate and includes a substrate support, a solder ejector that directs solder droplets to desired positions on the support, and an ejector aligner. The solder ejector is positioned relative to the substrate support to eject a stream of molten solder droplets for deposit onto the substrate. The ejector aligner is constructed and arranged to support the solder ejector in position for solder deposition. The aligner is constructed and arranged to adjust the orientation of the solder ejector in two angular dimensions to enable adjustment of the trajectory of the stream of molten solder droplets.
Embodiments may include one or more of the following features. The solder ejector includes a spherical surfaces and the aligner includes a corresponding spherical surface that slidably mates therewith, the spherical surfaces having centers that coincide with the orifice. The apparatus also includes a detection system for determining the trajectory of the ejected solder droplets. The detection system has detectors that determine angles of the ejected solder droplet trajectory with a vertical axis in two orthogonal planes. The detectors are located below a droplet deflection structure (e.g., electrical deflection plates used to deflect charged droplets).
Embodiments of the invention may include one or more of the following advantages. The trajectory of solder droplets can be easily and accurately oriented with respect to the substrate support to guarantee accurate alignment with the substrate support and with electrical deflection plates used to deflect charged droplets.
Other features and advantages will become apparent from the following description and from the claims.
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Balog Robert J.
Freeman Gary T.
Muntz Eric Phillip
Orme-Marmarelis Melissa E.
Pham-Van-Diep Gerald C.
Heinrich Samuel M.
Mintz Levin Cohn Ferris Glovsky and Popeo P.C.
Speedline Technologies, Inc.
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