Motorola Corporation

John L Leicht

William R Bratschun

James E Mitzlaff

Hugh Robert Malone

James A Wrezel

Douglas J Mathews

Scott D Munier

Vernon R Scott

Jeffrey D Leitheiser

Michele G Oehlerking

Solder pastes presently harden or congeal over time. This results in wasted solder paste and in production down time. This hardening is a result of the long polymer chains created by the dicarboxylic acid in the activator and the indium (In) or tin (Sn). A solder paste is described in which the metal alloy is coated by an agent that inhibits the reaction with the dicarboxylic acid. One solution involves coating the metal alloy powder with monocarboxylic acids, which truncate the polymer chain. Another manner for truncating the polymer is to coat the metal alloy powder with complexing agents. The metal alloy powder can also be coated by a stable metal such as lead (Pb), gold (Au), silver (Ag), bismuth (Bi), palladium (pd), platinum (Pt), a silver palladium alloy (AgPd) or a silver platinum alloy (AgPt).

Solder paste

An electronic assembly (100) includes multiple solder connections (101) coupling faying surfaces (202, 204) of two substrates (106, 108). A solder connection (201) is fabricated by reflow heating of a first, less compliant solder paste (312, 314) and a compliant preform (210) so as to cause compliant material of the preform (210) to dissolve into the solder paste (312, 314). Upon solidification of the solder paste (312, 314), blended regions (520, 522), having a gradual, changing concentration of compliant material form between resulting fillets (212, 214) and the preform (210). The blended regions (520, 522) transfer temperature induced shear stresses, caused by thermal cycling of the electronic assembly (100), from the fillets (212, 214) into the compliant preform (210).

Alloy solder connect assembly and method of connection

A method of welding two dissimilar metals of substantially different melting temperatures by passing an electric current through an interface created by biasing a projection located on the higher melting point metal into intimate contact with a surface located on the lower melting point material. The electrical current substantially liquifies a portion of only the second metal so that the projection is not substantially deformed by the welding operation.

Welding design for plated, dissimilar metals

A non-hermetic, three-dimensional, microwave semiconductor device carrier with integral waveguide couplers is disclosed. A molded plastic substrate having a suitable dielectric constant and varying thicknesses comprises plated conductors and locations for receiving GaAs MMIC's. MMIC's are mounted to a metal backplate and die bonded to the plated conductors. The waveguide couplers are integrally molded as part of the carrier substrate, and comprise plated through cylindrical members. Signals from a waveguide cavity are coupled to the MMIC's by inserting the waveguide couplers into a waveguide port. The carrier and integral waveguide coupler together with a plated molded cover forms a non-hermetic package providing pseudo-shielding cavities about the resident multiple semiconductor GaAs die. Transmission line impedance control is enhanced varying the substrate thickness on a per conductor basis. Frequency of operation exceeds 12 gigahertz.

Three-dimensional microwave circuit carrier and integral waveguide

Unique circuit location sensing apparatus for component placement robots (100) utilizes a high-resolution optical reflective sensor (110) for detecting the location of selected circuit runners (300, 301) on a printed circuit board (350). The sensor (110) is mounted to the robot arm (106) and coupled by A/D converting circuitry (104) to the robot computer (102). The robot computer (102) positions sensor (110) over a selected runner (300, 301) and steps sensor (110) across the selected runner (300, 301), storing the digitized sensor output for each step. The robot computer (102) processes the digitized sensor outputs to determine the actual location of the selected runner (300, 301) and then calculates location offsets for the component placement program to be subsequently run on the robot computer (102). As a result, variations in actual location of circuitry on different printed circuit boards (350) are automatically compensated for and components are more accurately placed thereon. The unique circuit location sensing apparatus of the present invention may be advantageously utilized in any component placement robot for accurately detecting the location of circuitry prior to placement of components on the printed circuit board.

Circuit location sensor for component placement apparatus

A solder paste dispensing assembly provides for the controlled application of a predetermined solder paste pattern to a surface. The surface can be on a printed circuit board, prior to or after the board is mounted onto an assembled product or it can be a portion of the product itself. The surface can be a planar or non-planar surface.

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Hawthorn Woods, IL, United States of America

John L Leicht