Abstract: A stencil used for printing solder paste on a contact pad of a printed wiring board has interior surfaces that define one or more apertures through the stencil. Those interior surfaces are coated with a material, such as parylene, having a lower surface tension than the interior surfaces absent the coating. The stencil can also have one or more reverse-tapered apertures passing there through, wherein the apertures have a variable cross-section that is larger at the fill side of the stencil (i.e., where solder paste enters the apertures) than at the board side of the stencil (i.e., where the stencil contacts the contact pad of the printed wiring board). Solder paste can be printed through the aperture(s) of the stencil onto contact pads on a printed wiring board.

Abstract: A process for removing patterned negative working resist from the surface of a substrate during manufacture of printed wiring boards is disclosed. The process includes the steps of contacting the patterned resist with a stripping solution containing an alkalinity source as well as a source of ammonium ions. The stripping solution is characterized in that it does not contain volatile organic compounds (VOCs).

Abstract: A method for applying an underfill and edge coating to a flip chip is described. The method includes the steps of adhering a bumped wafer to an expandable carrier substrate, sawing the wafer to form individual chips, stretching the carrier substrate in a bidirectional manner to form channels between each of the individual chips, applying an underfill material to the bumped surfaces of the chips and around the edges of the chips, cutting the underfill material in the channels between the chips and removing the individual, underfill coated chips from the carrier.

Abstract: In PCB manufacture, the pads and/or through-holes of a bare board are protected prior to mounting of other components by a silver plating process. The silver plate is applied from a plating composition by a replacement process in which silver ions oxidized copper and deposit a layer of silver at the surface. In the aqueous plating composition the silver ions are maintained in solution by the incorporation of a multidentate complexing agent. The compositions may contain a silver tarnish inhibitor and are free of reducing agent capable of reducing silver ions to silver metal, halide ions and substantially free of non-aqueous solvent. Surface mounted components can be soldered direct to the silver coated contact using any commercially available solder. Silver does not deposit onto solder mask, but only onto metal which is less electropositive than silver.

Abstract: A post-treatment method for copper on printed circuit boards is disclosed. The method comprises forming a cupric-based organometallic conversion coating on a copper surface of a printed circuit board, and then converting the cupric-based organometallic conversion coating to a cuprous-based organometallic conversion coating. The resulting cuprous-based organometallic conversion coating is desirable in that it improves copper to dielectric bond integrity.

Abstract: Mold compounds for encapsulating semiconductors are disclosed. The compounds achieve high levels of adhesion to uncleaned printed wiring board substrates by minimizing the level of silicone fluid in the compound. Methods for encapsulating semiconductor dies and processes for encapsulating the dies also are disclosed.

Abstract: A flip chip having solder bumps and an integrated flux and underfill, as well as methods for making such a device, is described. The resulting device is well suited for a simple one-step application to a printed circuit board, thereby simplifying flip chip manufacturing processes which heretofore have required separate fluxing and underfilling steps.

Abstract: A stencil holder assembly comprising a stencil plate connector and a stencil plate for use with a stencil printer in single component solder paste applications. The stencil plate connector is mounted onto the stencil printer for the duration of operation of the stencil printer and stencil plates are removably mounted thereon by means of an adapter centrally mounted on the stencil plate. Solder paste stencil patterns are readily interchanged onto the stencil printer during solder paste applications by mounting and removing stencil plates from the stencil plate connector.

Abstract: A stencil and stencil identification system in which the stencil carries a tagging device capable of storing data corresponding to characteristics of the stencil and the pattern of apertures formed in the stencil. The stencil with tagging device may be utilized in combination with a stencil printing device having a tag reader which reads information data stored within the tagging device and/or writes information into the tagging device relating to characteristics of the stencil or other criteria.

Abstract: A two-stage accelerator for use in filled anhydride/epoxy systems is disclosed. In particular, the present invention makes use of a first accelerator to initiate curing of the epoxy while the filler becomes wetted, and a second, faster accelerator to complete the curing process.

Abstract: A method and apparatus for more efficiently depositing a gas onto a surface. In one embodiment, a deposition apparatus is provided. The deposition apparatus comprises a deposition chamber, a tube and a heating element. The tube is in fluid communication with the deposition chamber, and the heating element is constructed and arranged so that the heating element preferentially heats the centerline of the tube relative to the inner surface of the tube. In another embodiment, a method of depositing a product gas onto a surface is provided. The method comprises placing a first gas into a tube; heating first and second portions of the first gas to first and second temperatures, respectively, to form the product gas, the first portion of the first gas being adjacent the centerline of the tube, the second portion of the first gas being adjacent the inner surface of the tube, the first temperature being greater than the second temperature; and depositing the product gas onto the surface.

Abstract: An indicator for complete polymerization and cure of base-catalyzed epoxy thermoset resin systems is disclosed. In particular, the present invention makes use of an diazo dye having amino groups which forms a salt or complex with hardeners used in various epoxy resin systems. Upon full polymerization and consumption of the hardener, a chromophoric shift of the dye can be observed.

Abstract: In PCB manufacture, the pads and/or through-holes of a bare board are protected prior to mounting of other components by a silver plating process. The silver plate is applied from a plating composition by a replacement process in which silver ions oxidized copper and deposit a layer of silver at the surface. In the aqueous plating composition the silver ions are maintained in solution by the incorporation of a multidentate complexing agent. The compositions may contain a silver tarnish inhibitor and are free of reducing agent capable of reducing silver ions to silver metal, halide ions and substantially free of non-aqueous solvent. Surface mounted components can be soldered direct to the silver coated contact using any commercially available solder. Silver does not deposit onto solder mask, but only onto metal which is less electropositive than silver.

Abstract: Multi-level structures including a first layer with a parylene polymer layer deposited thereon. The parylene polymer layer has the structure: ##STR1## m is an integer having a value of 0, 1, 2, 3 or 4, and z is greater than 1. G is a halogen, an alkyl group, a cyclo hydrocarbon, an alkylene group or an alkylyne group having the general formula C.sub.n H.sub.y X.sub.w. X is a halogen, and n is an integer greater than zero. The sum of y and w is at most equal to a 2n+1. The parylene polymer layer can have a zinc impurity level of about 66 parts per billion or less. The parylene polymer layers are formed by a process in which monomers are formed outside of a deposition zone of a vacuum chamber. The monomers may be prepared by a process in which a parylene dimer is vaporized and subsequently pyrolized. The process may further include the step of passing the vapor through a post-pyrolysis zone prior to depositing the monomer on the substrate.

Abstract: Improved cleaning compositions for the removal of various forms of contamination from printed circuit boards and other related electronic equipment in vapor cleaning processes are disclosed, including major amounts of 1,1,1-trichloroethane and an amount of normal propanol less than that in the true azeotropic mixture of these components, generally from about 1.0 to less than 4.75 weight percent of the normal propanol. In addition, vapor cleaning processes utilizing such solvent compositions are also disclosed, and in a preferred embodiment, the composition includes about 96.0 weight percent of the 1,1,1-trichloroethane and about 4.0 weight percent of the normal propanol.

Abstract: The gas supplied to a foam fluxer utilized for wave soldering is presaturated with a flux thinner compatable with the flux solvent utilized in the foam fluxer to eliminate evaporation of solvent in the foam fluxer and maintain the temperature and specific gravity of the flux solution constant.

Abstract: An apparatus for determining the quantitative presence of ions derived from solids, liquids, gases or similar items in which a deionized liquid dissolves the ions from the items, the liquid then is evaluated for conductivity by virtue of the presence of the ions, the liquid is then passed through a deionizer to substantially remove the ions, and again the liquid is re-exposed to the partially cleansed item; the cycle is continued until conductivity indicates that a predetermined degree of deionization has been achieved.

Abstract: A solder alloy for use in automated soldering of workpieces by application thereto of liquid solder from a molten reservoir. The alloy consists essentially of from about 50 to 57.5% by weight tin, from about 1.5 to 4% by weight antimony, with the balance being substantially lead. The alloy is preferably further characterized in displaying a solidus-to-liquidus temperature range no greater than that of a 60/40 weight ratio tin/lead solder.

Abstract: .[.A solder alloy for use in automated soldering of workpieces by application thereto of liquid solder from a molten reservoir. The alloy consists essentially of from about 50 to 57.5% by weight tin, from about 1.5 to 4% by weight antimony, with the balance being substantially lead. The alloy is preferably further characterized in displaying a solidus-to-liquidus temperature range no greater than that of a 60/40 weight ratio tin/lead solder..]..Iadd.An improved process for machine soldering a workpiece by application thereto of a liquid solder from a molten reservoir is disclosed. The improvement resides in the use of solder alloys having a composition of approximately 55% tin, 2.77% antimony, the remainder being substantially lead or approximately 52% tin, 3% antimony, the remainder being substantially lead..Iaddend.