Abstract: A stepped multilayer Printed Wiring Board (PWB) (10), having an increased number of wiring paths in selected regions, is comprised of a main multilayer PWB (12) having a sufficient number of layers (12.sub.1,12.sub.2,12.sub.3 . . . 12.sub.n) to provide the lowest number of wiring paths required anywhere on the board. In regions where a larger number of wiring paths are required, a secondary, multilayer PWB section (22), having a sufficient number of layers (22.sub.1,22.sub.2,22.sub.3) to provide the required additional number of wiring paths, is connected to the main PWB by a layer of anisotropically conductive material (30) sandwiched therebetween. A plurality of mechanical fasteners (33,33'), typically bifurcated or heat-staked plastic pins, extends through the secondary PWB section and the main PWB to hold one to the other.

Abstract: Interconnection of each of a plurality of bond sites (14) on a semiconductor chip (10) to a corresponding one of a plurality of metallized areas (16) on a substrate (12) is accomplished via a sheet of anisotropically conductive material (18) sandwiched therebetween. The anisotropically conductive material advantageously has a cutout (24) therein located to expose at least a portion of the substrate lying between a pair of metallized areas (16). The cutout (24) serves to confine a quantity of adhesive (26) deposited therein which serves to secure the chip to the substrate without any physical bond between the metallized areas and the bond sites on the chip while maintaining the anisotropically conductive material in compression.

Abstract: An apparatus (28) for dispensing solder paste into openings (26-26) in a stencil (24) comprises a housing (30) having a piston (60) slidably mounted therein. A manifold (70), having a successively increasing cross-sectional area, is attached to a side wall (42) of the housing for admitting a viscous material, such as solder paste therein through successively larger sized openings (76-76) so the paste is distributed evenly beneath the piston. A pair of elastomeric blades (50-50) are secured to, and depend from the housing on opposite sides of a slot (46) to contact the stencil (24). Upon the application of a fluid pressure against the piston, paste will be expelled from the slot within a working region (96) between the blades. The blades force paste into the openings in the stencil when the housing is moved thereacross.

Abstract: A multipoint dispensing of viscous material onto a board (23) comprises the monitoring and controlling of several process parameters such as the initial gap (.delta.) between a dispensing tool (20,25) and the board (23), the dispense pressure time cycle within the tool (FIG. 3A) and the tool velocity cycle (FIG. 3B). Also, an improved method for loading solder paste into the dispensing tool includes applying vacuum to two regions of the tool while vibrating it in its axial direction (FIG. 4). Furthermore, improved techniques for preventing crust formation on the paste within the tool, and for controlling the viscosity of the solder paste within the tool, achieve consistent dispensing results in a production environment.

Abstract: A multipoint dispensing of viscous material onto a board (23) comprises the monitoring and controlling of several process parameters such as the initial gap (.delta.) between a dispensing tool (20,25) and the board (23), the dispense pressure time cycle within the tool (FIG. 3A) and the tool velocity cycle (FIG. 3B). Also, an improved method for loading solder paste into the dispensing tool includes applying vacuum to two regions of the tool while vibrating it in its axial direction (FIG. 4). Furthermore, improved techniques for preventing crust formation on the paste within the tool, and for controlling the viscosity of the solder paste within the tool, achieve consistent dispensing results in a production environment.

Abstract: A tapered array of apertures are provided in a wall of a solder pot to permit passage of molten solder therethrough. Molten solder is pumped along an outside channel, perpendicular to the axes of the apertures, and through the apertures to cause the solder pot to overflow with a uniformly distributed wave. The array tapers in the direction of pumped fluid flow.