Abstract: A microelectronic package (10) is formed by placing a lead frame (22) onto an adhesive polyimide tape (38). The lead frame (22) includes a plurality of metallic leads (16) and an opening. An integrated circuit die (12) is positioned onto the molding support (38) within the opening such that a non-active face (32) of the integrated circuit die (12) rests against the molding support (38). Wire leads (18) connect an active face (28) of the integrated circuit die (12) to the metallic leads (16). A plurality of metallic bumps (20) are attached to the metallic leads (16), and a polymeric precursor is dispensed. The precursor embeds the active face (28) of the integrated circuit die (12), the inner surface (19) of the metallic leads (16), the wire leads (18), and the metallic bumps (20). The microelectronic package (10) is then heated to cure the polymeric precursor to form a polymeric body (14).

Abstract: A microelectronic package (10) is formed and includes an integrated circuit die (12) attached to a substrate (14) by a plurality of solder bump interconnections (16) to form a preassembly (18). The integrated circuit die (12) has an active face (20) that faces the substrate (14) and is spaced apart therefrom by a gap (22). The integrated circuit die (12) also includes a back face (24) opposite the active face (20). The substrate (14) includes a die attach region (26) and a surrounding region (28) about the integrated circuit die (12). The solder bump interconnections (16) extend across the gap (22) and connect the integrated circuit die (12) and the substrate (14). A mold (30) is disposed about the preassembly (18) such that the mold (30) cooperates with the substrate (14) to define a mold cavity (32) that encloses the integrated circuit die (12).

Abstract: A microelectronic package (10) is formed and includes an integrated circuit die (12) attached to a substrate (14) by a plurality of solder bump interconnections (16) to form a preassembly (18). The integrated circuit die (12) has an active face (20) that faces the substrate (14) and is spaced apart therefrom by a gap (22). The integrated circuit die (12) also includes a back face (24) opposite the active face (20). The substrate (14) includes a die attach region (26) and a surrounding region (28) about the integrated circuit die (12). The solder bump interconnections (16) extend across the gap (22) and connect the integrated circuit die (12) and the substrate (14). A mold (30) is disposed about the preassembly (18) such that the mold (30) cooperates with the substrate (14) to define a mold cavity (32) that encloses the integrated circuit die (12).

Abstract: A microelectronic package (10) is formed by placing a lead frame (22) onto an adhesive polyimide tape (38). The lead frame (22) includes a plurality of metallic leads (16) and an opening. An integrated circuit die (12) is positioned onto the molding support (38) within the opening such that a non-active face (32) of the integrated circuit die (12) rests against the molding support (38). Wire leads (18) connect an active face (28) of the integrated circuit die (12) to the metallic leads (16). A plurality of metallic bumps (20) are attached to the metallic leads (16), and a polymeric precursor is dispensed. The precursor embeds the active face (28) of the integrated circuit die (12), the inner surface (19) of the metallic leads (16), the wire leads (18), and the metallic bumps (20). The microelectronic package (10) is then heated to cure the polymeric precursor to form a polymeric body (14).

Abstract: A selectively filled thermally curable adhesive film (10) contains a fluxing agent for reflow soldering an electronic device to a substrate. The adhesive film has a central, region (12) and a boundary region (14) surrounding the central region. The central region consists of an adhesive that is filled with an inert filler to reduce the co-efficient of thermal expansion of the adhesive. The boundary region consists of an unfilled adhesive and a fluxing agent. The film may be used to adhesively bond a flip chip semiconductor die (20) to a substrate (21). When solder bumps (22) on the die are reflowed, the fluxing agent acts to remove any oxides present on the solderable surfaces of the substrate or the die.

Abstract: The present invention provides a method for forming a solder bump (24) on a substrate (20). The substrate (20) includes a bond pad (18) having a faying surface (19) composed of solder-wettable metal. The method includes coating the faying surface (19) with a plate (16) formed of a first metal having a first melting temperature, and projecting a discrete microdroplet (14) onto the plate (16). The microdroplet (14) is formed of a molten second metal and has a second melting temperature greater than the first melting temperature. The microdroplet (14) fuses to the plate (16) to form the solder bump (24).

Abstract: An electronic package comprises a component mounted on a substrate, such as a printed circuit board, by a solder connection that is based upon a tin alloy containing zinc. The connection is formed to copper faying surface on the substrate, and includes a first layer formed of a zinc-free tin metal bonded to the copper surface and a second layer formed of the tin-zinc solder alloy bonded to the first layer. The first layer provides a zinc-free barrier between the copper and the tin-zinc alloy to retard zinc migration to the copper interface that would otherwise result in dezincification of the solder alloy and reduce the mechanical properties of the connection.

Abstract: An electroless immersion plating process for depositing a tin-bismuth plate onto a surface formed of copper or the like comprises immersing the surface into an acidic aqueous solution comprising a tin alkane sulfonate compound, preferably tin methane sulfonate, and a bismuth alkane sulfonate compound, preferably bismuth methane sulfonate. The solution also contains thiourea in an amount effective to reduce tin at the surface. The bismuth compound is added in an amount to produce a bismuth concentration that is less than about 1.0 gram per liter. Furthermore, the ratio of tin to bismuth in the solution is at least 30 to 1, and preferably at least 50 to 1. The process deposits a dense, adherent plate composed of a tin-bismuth alloy containing at least 50 weight percent tin and preferably containing greater than 70 weight percent tin, which plate is well suited for use in microelectronic soldering operations.

Abstract: A solder paste of the type utilized in forming a solder onnectin for a microelectronic package comprises a mixture of compositionally distinct metal powders. The paste comprises a first metal powder formed of tin-bismuth solder alloy. The paste further comprises a second metal powder containing gold or silver. During reflow, the gold or silver alloys with the tin-bismuth solder to increase the melting part and enhance mechanical properties of the product connection.

Abstract: An electroless immersion plating process for depositing a tin-bismuth plate onto a surface formed of copper or the like comprises immersing the surface into an acidic aqueous solution comprising a tin alkane sulfonate compound, preferably tin methane sulfonate, and a bismuth alkane sulfonate compound, preferably bismuth methane sulfonate. The solution also contains thiourea in an amount effective to reduce tin at the surface. The bismuth compound is added in an amount to produce a bismuth concentration that is less than about 1.0 gram per liter. Furthermore, the ratio of tin to bismuth in the solution is at least 30 to 1, and preferably at least 50 to 1. The process deposits a dense, adherent plate composed of a tin-bismuth alloy containing at least 50 weight percent tin and preferably containing greater than 70 weight percent tin, which plate is well suited for use in microelectronic soldering operations.

Abstract: An electronic package comprises a component mounted on a substrate, such as a printed circuit board, by a solder connection that is based upon a tin alloy containing zinc. The connection is formed to copper faying surface on the substrate, and includes a first layer formed of a zinc-free tin metal bonded to the copper surface and a second layer formed of the tin-zinc solder alloy bonded to the first layer. The first layer provides a zinc-free barrier between the copper and the tin-zinc alloy to retard zinc migration to the copper interface that would otherwise result in dezincification of the solder alloy and reduce the mechanical properties of the connection.

Abstract: A solder paste of the type utilized in forming a solder onnectin for a microelectronic package comprises a mixture of compositionally distinct metal powders. The paste comprises a first metal powder formed of tin-bismuth solder alloy. The paste further comprises a second metal powder containing gold or silver. During reflow, the gold or silver alloys with the tin-bismuth solder to increase the melting part and enhance mechanical properties of the product connection.

Abstract: A solder bump interconnection (34) bonding a metal bump (30) affixed to an integrated circuit component (10) to a terminal pad (18) of a printed circuit board (12) is formed using a consumable path (24) and a solder deposit (28) applied to the path spaced part from the terminal pad. In addition to the terminal pad, the printed circuit board includes a solder-nonwettable surface (21). The consumable path extends from the terminal pad on the solder-nonwettable surface and is formed oa solder-soluble metal. The solder deposit is heated, preferably by a laser beam, to form molten solder that is drawn along the pathdissolving the path as it proceeds. At the terminalmolten solder wets the pad and the metal bump and solidifies to complete the inerconnection.

Abstract: An integrated circuit component is attached to a printed circuit board by solder bump interconnections that are formed between metal bumps on the component and a metal-plated terminal on the board. The metal plate overlies both a bond pad and an adjacent runner of each terminal and is formed of a first metal, which is preferably a tin-base alloy. The metal bumps on the component are formed of a second metal, which is preferably an indium-base alloy. The component and board are assembled and heated to a temperature less than the melting temperatures of the first and second metals. At the interface between the bumps and the plate, the first and second metals cooperate to form a liquid phase which, upon cooling and solidifying, completes the interconnection.

Abstract: An improved electrical component package comprises a component attached to a substrate by a plurality of multisolder interconnections. Each interconnection comprises a preformed spacer bump composed of a first solder alloy, preferably a lead-base tin alloy containing greater than 90 weight percent lead. The spacer bump is directly metallurgically bonded to a metallic electrical contact of the component and rests against a corresponding metallic electrical contact of the substrate, but is not bonded thereto. Each interconnection further comprises a sheath portion formed of a second compositionally distinct solder alloy having a liquidus temperature less than the first alloy solidus temperature. A preferred second solder is a tin-lead alloy comprising between about 30 and 50 weight percent lead and the balance tin or indium.

Abstract: A low temperature-wetting solder paste for forming a tin-base solder connection comprises a mixture of compositionally distinct first and second solder powders. The first solder is formed predominantly of tin, preferably at least 90 weight percent. The second powder is formed of a tin alloy containing indium or bismuth and having a melting temperature less than the first powder. During soldering, the second powder melts during the early stages of the heating cycle to initiate wetting of the faying surfaces and promote dissolution of the first powder, thereby reducing the time and temperature required to form the solder connection.

Abstract: A solder connection (30) is formed based upon a tinindium or tin-bismuth alloy, but having a melting temperature greater than the melting temperature of the initial solder alloy. A deposit (26) of solder alloy is placed against a tin plate (24) applied, preferably by electrodeposition, to a first faying surface (18). Following assembling with a second faying surface (22), the assembly is heated to melt the solder deposit, whereupon tin from the tin plate dissolves into the solder liquid to form a tin-enriched alloy having an increased melting temperature.

Abstract: An improved electrical component package comprises a component attached to a substrate by a plurality of multisolder interconnections. Each interconnection comprises a preformed spacer bump composed of a first solder alloy, preferably a lead-base tin alloy containing greater than 90 weight percent lead. The spacer bump is bonded to a metallic electrical contact of the component and rests against a corresponding metallic electrical contact of the substrate, but is not directly metallurgically bonded thereto. Each interconnection further comprises a sheath portion formed of a second compositionally distinct solder alloy having a liquidus temperature less than the first alloy solidus temperature. A preferred second solder is a tin-lead alloy comprising between about 30 and 50 weight percent lead and the balance tin or indium.

Abstract: A body formed of a lead-tin solder alloy is pretreated to deposit palladium thereon prior to soldering to a metallic substrate. It is found that the palladium deposit enhances wetting of the substrate by the solder liquid during reflow and thereby, upon cooling, produces a strong metallurgical bond. In a preferred embodiment, lead-tin solder balls are pretreated by applying tin-palladium colloidal particles and dissociating the particles to form a discontinuous metallic palladium deposit.