Abstract:
A lead free solder hierarchy for use in the second level solder connection of electronic components such as joining an electronic module (20) to a circuit board (120). An off-eutectic solder (60) concentration of SnCu or SnAg is used for the module side connection. This off-eutectic solder (60) contains sufficient intermetallics to provide the module side connection with a robust second level assembly and rework process. The off-eutectic composition (60) provides an intermetallic phase structure in the module side fillet during assembly. The intermetallic phase structure eliminates problems of tilt and collapse during second level assembly and aids in rework by providing a more cohesive joint allowing removal of the columns (100) from the board (120) without simultaneous removal from the module (20).
Abstract:
A ball grid array package utilizes solder balls (14) having central cores of a material with a higher melting point than solder material surrounding the core. When the ball grid package (12) and motherboard assembly (10) are heated to the melting point of the solder material, the cores remain solid and function as spacers in preventing direct contact of the package surface and the motherboard surface, thus preventing molten solder from being squashed and flowing to adjacent ball contacts.
Abstract:
An interconnector (10) is provided that improves the reliability of an electrical and mechanical connection between two substrates (16, 18). An interconnector (10) according to the invention includes a compliant core (12) surrounded by an electrically conductive layer (14).
Abstract:
A ball grid array device (10) utilizes solder balls (24) comprised of a core (34) having a relatively high melting temperature and a solder coating (30) having a lower melting temperature. The core (34) may be metal, a polymer or a metal-coated polymer.
Abstract:
Disclosed is a connector structure on a substrate (10) which includes at least one first solder portion (16) on the surface of the substrate; at least one second solder portion (18) connected to each of the at least one first solder portions; and an epoxy layer (20) disposed about the at least one first and second solder portions in such a manner as to cover the first solder portion and contact, but not cover, the second solder portion. Also disclosed is a connector structure on a substrate which includes at least one first solder portion on the surface of said substrate; at least one second solder ball portion connected to the at least one first solder portions; wherein the melting point of the second solder ball portion is relatively higher than that of the first solder portion. Finally, disclosed is a method of testing the solderability of the above structures.
Abstract:
A method of forming solder bumps includes the steps of applying a thick layer of solder resist (22) to a substrate (20). The resist is selectively removed to provide wells (23) at solder pads (21) on the substrate. The solder paste (24) is applied to the substrate in the wells. The solder paste is reflowed to form solder bumps (25) on the pads. A socket for a solder bumped member (36) is obtained by first providing a substrate (30) having metallized pads corresponding to the solder bumps of the member. A thick layer of photo definable solder resist (32) is applied to the substrate. The resist is selectively removed to provide wells (33) at the metallized pads (31) of the substrate. Solder paste (34) is then deposited in the wells. The solder bumped member (36) can then be positioned so that the solder bumps (37) are located in the wells. The solder paste (34) is reflowed to bond to the solder bumps (37) and the metallized pads (31). The solder paste (34) can be selected to have a lower melting temperature than the solder bumps (37). By reflowing the solder paste (34) at a temperature lower than the melting temperature of the solder bumps (37), the paste can wet to and blend with the solder bumps while not causing the solder bumps to reflow.
Abstract:
A laminated structure is formed by providing metal layers having wettability relative to solder at least on both sides and by inserting at least one layer of a metal which can control the diffusion of the solder between them. The terminals for connection between the substrates having structure in which a pair of solder bumps are adhered onto both surfaces of the laminated structure, and a method of producing the same are given.
Abstract:
A dual solder layer for fluidic self assembly, an electrical component substrate, and method employing same is described. The dual solder layer comprises a layer of a self-assembly solder disposed on a layer of a base solder which is disposed on the solder pad of an electrical component substrate. The self-assembly solder has a liquidus temperature less than a first temperature and the base solder has a solidus temperature greater than the first temperature. The self-assembly solder liquefies at the first temperature during a fluidic self assembly method to cause electrical components to adhere to the substrate. After attachment, the substrate is removed from the bath and heated so that the base solder and self-assembly solder combine to form a composite alloy which forms the final electrical solder connection between the component and the solder pad on the substrate.