摘要:
A multi-layer flexible circuit board has multiple thicker regions to which components are mounted and thinner, more flexible regions with fewer wiring layers through which the board can be bent about a line without bending thicker regions. Surface mount components such as QFP's and flip-chips are mounted on the front side, and surface mount and pin-in-hole components are mounted on the back side of the circuit board at the thick regions. Heat spreaders are laminated to the back sides of thicker regions. The thicker regions have windows in which wire bond chips are mounted on the heat spreader and wire bonded to the front side of the board. A thermally conductive adhesive or grease connects between the tops of the back side components and the bottoms of the cavities. The heat sinks are bolted together and/or to an enclosure frame to improve thermal performance.
摘要:
A screen printing fixture holds a flexible circuit board having components attached to one side, to allow screening a pattern of solder paste onto the second side for subsequent attachment of components to that side. In an electronic package assembly a flexible circuit board with components is wound about a heat spreader assembly having a cavity so that at least one component on the flexible circuit board is positioned within the cavity and in thermal connection to the heat spreader.
摘要:
A multi-layer flexible circuit board has thicker regions to which surface-mount-technology (SMT) components (such as flip chips and QFPs) and pin-in-hole (PIH) components are mounted on both sides and which contains conductive through vias between wiring layers. After the SMT components have been mounted to the first side, a screening fixture with a support surface that has cavities conforming the components on the first side, is used to screen solder paste to the other side of the board. The thicker regions are surrounded by thinner regions of the board with fewer wiring layers and preferably fewer or thinner dielectric layers, and which can be bent along a line without bending the thicker regions. A common heat spreader plate with cavities or holes for multiple components is laminated to the thicker regions on one side of the board. The thicker regions have windows in which wire-bond chips are mounted to the heat spreader and the chips are wirebonded to the other side of the board. A thermally conductive adhesive or grease connects between the components and the bottoms of the cavities. Two heat sink plates are bolted together and along with other such heat sink plates are bolted to an enclosure frame to improve thermal performance.
摘要:
A screen printing machine comprising a backing plate with holes conforming to components attached to the surface of a flexible circuit board. The machine includes a screen which patterns solder paste on the surface of the circuit board while the circuit board is on the backing plate. Also included is a spring loaded element disposed adjacent to the backing plate which applies a predetermined continuous force to the four corners of the circuit board. This force is applied in a diagonal direction to the corners to stretch the circuit board so that the circuit board is parallel to the backing plate during screening.
摘要:
A method of applying bonding agents, such as solder pastes and conductive adhesives, to pad sites in the manufacture of electronic circuits uses a paste injection head. A permanent mask with cavity openings is applied around conductive pads on a carrier. The conductive pads correspond to chip attachment sites. The injection head is brought into contact with a surface of the mask, and pressure is applied to a bonding agent in the injection head. The injection head is then moved over the surface of the mask, filling cavity openings with the bonding agent. The injection head is then removed from the surface of the mask. If a solder paste is used, infrared radiation is applied to filled cavity openings to evaporate a paste flux and reflow solder to form solder balls within the cavity openings projecting above the mask. If a conductive adhesive is used, a stencil is applied to the surface of the mask prior to contacting the mask with said injection head. When the cavity openings are filled, stencil is removed from the mask and the conductive adhesive filling the cavity openings is dried.
摘要:
A method of applying bonding agents, such as solder pastes and conductive adhesives, to pad sites in the manufacture of electronic circuits uses a paste injection head. A permanent mask with cavity openings is applied around conductive pads on a carrier. The conductive pads correspond to chip attachment sites. The injection head is brought into contact with a surface of the mask, and pressure is applied to a bonding agent in the injection head. The injection head is then moved over the surface of the mask, filling cavity openings with the bonding agent. The injection head is then removed from the surface of the mask. If a solder paste is used, infrared radiation is applied to filled cavity openings to evaporate a paste flux and reflow solder to form solder balls within the cavity openings projecting above the mask. If a conductive adhesive is used, a stencil is applied to the surface of the mask prior to contacting the mask with said injection head. When the cavity openings are filled, stencil is removed from the mask and the conductive adhesive filling the cavity openings is dried.
摘要:
A method of applying bonding agents, such as solder pastes and conductive adhesives, to pad sites in the manufacture of electronic circuits uses a bonding agent injection head which includes a wiping guide, a blade which cooperates with the wiping guide to form an elongate nozzle slit, and an evacuation path ahead of the nozzle slit in a direction of movement of the injection head. A permanent mask with cavity openings is applied around conductive pads on a carrier. The conductive pads correspond to chip attachment sites. The injection head is brought into contact with a surface of the mask, and pressure is applied to a bonding agent in the injection head. The injection head is then moved over the surface of the mask, filling cavity openings with the bonding agent. The evacuation path ahead of the nozzle slit lets air out of the cavity openings as the cavity openings are filled with bonding agent. The injection head is then removed from the surface of the mask. If a solder paste is used, infrared radiation is applied to filled cavity openings to evaporate a paste flux and reflow solder to form solder balls within the cavity openings projecting above the mask. If a conductive adhesive is used, a stencil is applied to the surface of the mask prior to contacting the mask with said injection head. When the cavity openings are filled, the stencil is removed from the mask and the conductive adhesive filling the cavity openings is dried.
摘要:
A method for bonding heat sinks to packaged electronic components comprises the steps of: (a) exposing to a plasma a surface of a molded polymer formed on a substrate; (b) allowing the plasma to at least partially convert silicon-containing residue on the surface to silica; and (c) bonding an article to the surface by applying an adherent between the article and the surface. Often, the silicon-containing residue is silicone oil, a mold release compound, which may prevent the formation of a bond when using conventional bonding methods and materials. The silica layer formed on the surface of the molded polymer assists in formation of a proper bond. The plasma may be an oxygen plasma and the adherent may be selected from either a heat cured silicone-based paste adhesive with a metal oxide filler or a heat cured porous polymer film impregnated with adhesive. In particular, the film may be polytetrafluoroethylene, the adhesive may be polybutadine, and the film may be further impregnated with a metal oxide heat transfer medium, such as zinc oxide. An alternate method comprises applying the porous polymer film without plasma treatment and heat curing the film to form a proper bond.
摘要:
A method for bonding heat sinks to packaged electronic components comprises the steps of: (a) exposing to a plasma a surface of a molded polymer formed on a substrate; (b) allowing the plasma to at least partially convert silicon-containing residue on the surface to silica; and (c) bonding an article to the surface by applying an adherent between the article and the surface. Often, the silicon-containing residue is silicone oil, a mold release compound, which may prevent the formation of a bond when using conventional bonding methods and materials. The silica layer formed on the surface of the molded polymer assists in formation of a proper bond. The plasma may be an oxygen plasma and the adherent may be selected from either a heat cured silicone-based paste adhesive with a metal oxide filler or a heat cured porous polymer film impregnated with adhesive. In particular, the film may be polytetrafluoroethylene, the adhesive may be polybutadine, and the film may be further impregnated with a metal oxide heat transfer medium, such as zinc oxide. An alternate method comprises applying the porous polymer film without plasma treatment and heat curing the film to form a proper bond.
摘要:
A method and device for testing and burning-in semiconductor circuits. The method and device permit the entire wafer to be tested by temporarily attaching the wafer to a test substrate using electrically conductive adhesive (ECA). The ECA conforms to deviations from co-planarity of the contact points of both the wafer and test substrate while providing a quality electrical connection at each point. ECA material can be deposited on either the wafer contacts or the substrate pads. In addition, the ECA may be deposited on C4 bumps or tin-capped lead bases. Variations in the method and device include filling vias of a non-conductive interposer with ECA. The electrical connection may be enhanced by forming conductive dendrites on test pads while the ECA is deposited on the wafer contacts. To further enhance the electrical connection, the ECA material can be plasma etched to remove some of its polymer matrix and to expose the electrically conductive particles on one side and then plating with palladium. After the palladium-plated ECA is brought into contact with aluminum pads, palladium-coated aluminum pads, or even C4 solder bumps, conductive dendrites are formed on the palladium-treated ECA bumps.