Lead frame attachment for optoelectronic device

Abstract

An optoelectronic device is mounted on a planar substrate in electrical connection with solder bumps adjacent an edge of the substrate and connection to a lead frame is made by loading the edge of the substrate on a lead frame support with lead frame conductors in engagement with the solder bumps and applying heat to melt the solder.

1 . A method of connecting an optoelectronic device to a lead frame assembly comprising mounting the optoelectronic device on a planar substrate having electrical connecting circuitry for connection to the optoelectronic device, connecting said device to said connecting circuitry, providing a plurality of solder bumps on a major face of the substrate adjacent an edge of the face, the solder bumps being in electrical connection with said connecting circuitry, mounting the substrate on a lead frame support which engages said major face adjacent its periphery, said lead frame support having lead frame conductors exposed on said support so as to contact said solder bumps, and applying heat to melt the solder and thereby form secure electrical connections between the lead frame conductors and the solder bumps.  
     
     
         2 . A method according to    claim 1    in which heat to melt the solder is applied to a plurality of solder bumps simultaneously to bond the bumps to respective lead frame conductors in a single operation.  
     
     
         3 . A method according to    claim 1    in which said lead frame support forms part of a casing which is positioned around the substrate and which is sealed to enclose the optoelectronic device.  
     
     
         4 . A method according to    claim 3    in which the lead frame support forms part of a mould which surrounds the substrate and the method includes moulding encapsulating material in the mould around the optoelectronic device and substrate to form a sealed product.  
     
     
         5 . A method according to    claim 1    in which the solder bumps are located on a peripheral region of the substrate between the optoelectronic device and said edge of the face so as to overlie the lead frame conductors when positioned on the lead frame support.  
     
     
         6 . A method according to    claim 5    in which the solder bumps are provided on the same major face of the substrate as the optoelectronic device and said substrate is inverted to locate the solder bumps under the substrate when the substrate is mounted on the lead frame support.  
     
     
         7 . A method according to    claim 5    in which pressure as well as heat is applied to urge the substrate into engagement with the lead frame support to cause the solder bumps to form secure electrical connection with the lead frame conductors.  
     
     
         8 . A method according to    claim 5    in which thermal access passages are provided through the thickness of said substrate adjacent said solder bumps and heat is transferred through said passages to melt the solder when connecting the substrate to the lead frame.  
     
     
         9 . A method according to    claim 5    in which thermal access passages are provided through the lead frame support and heat is transferred through the passages in the lead frame support to melt the solder when connecting the substrate to the lead frame.  
     
     
         10 . A method according to    claim 1    in which the substrate comprises a rigid support providing a connection of fixed relationship of position and direction between an optical fibre and an integrated optical waveguide device including at least one optoelectrical light source or receiver and forming at least part of said optoelectronic device.  
     
     
         11 . A method according to    claim 10    in which the optoelectronic device comprises an integrated silicon chip providing an optical waveguide and including an optoelectrical light source and/or receiver.  
     
     
         12 . A method according to    claim 10    in which the substrate is a ceramic substrate.  
     
     
         13 . A optoelectronic assembly comprising a planar substrate having electrical connecting circuitry, and an optoelectronic device mounted on said planar substrate and having electrical connection to said electrical connecting circuitry, said substrate being provided with a plurality of solder bumps on a major face of the planar support adjacent an edge of the planar support, said solder bumps being in electrical connection with said electrical connecting circuitry, whereby said assembly may be located on a lead frame support with said solder bumps in engagement with lead frame conductors for securing thereto by application of heat.  
     
     
         14 . An optoelectronic assembly according to    claim 13    in which said solder bumps are provided on a peripheral region of a major face of the substrate and located between the optoelectronic device and said edge of the support.  
     
     
         15 . An assembly according to    claim 14    in which thermal conducting passages are provided through the planar support adjacent said solder bumps.  
     
     
         16 . An optoelectronic assembly according to    claim 14    together with a lead frame assembly comprising a lead frame support with a plurality of lead frame conductors thereon, said support engaging the solder bumps of the planar substrate so that the lead frame conductors are secured to respective solder bumps by heat treatment of the solder bumps.  
     
     
         17 . An assembly according to    claim 16    in which securing means are located between edge regions of the substrate and the lead frame support to secure the substrate in position on the support.  
     
     
         18 . An optoelectronic assembly according to    claim 16    in which the lead frame support forms part of a casing which is positioned around the substrate and which is sealed to enclose the optoelectronic device.  
     
     
         19 . An assembly according to    claim 18    in which the lead frame support forms part of a mould surrounding the substrate, said mould containing encapsulating material around the optoelectronic device and substrate to form a sealed product.  
     
     
         20 . An assembly according to    claim 16    in which the solder bumps are located on the same face of the substrate as the optoelectronic device and said substrate is inverted to locate the solder bumps under the substrate in engagement with the lead frame conductors.  
     
     
         21 . An assembly according to    claim 16    in which thermal access passages are provided through the lead frame support for the transfer of heat to the solder bumps during connection of the bumps to the lead frame conductors.