High density electronic interconnection
View Patent ↗This is an interconnection between electronic devices and other assemblies (e.g. printed circuits). The electronic devices are mounted on high temperature insulating bases, such as ceramic substrates. The insulating base has a conductive pattern to connect the electronic device to another assembly. The conductive pattern terminates in metal bumps capable of being connected to another assembly (e.g. a printed circuit) by a conductive adhesive or metallurgically by soldering, thermocompression, thermosonic or ultrasonic bonding. The bumps are formed by applying a metal with a melting point over 350° C. to contact pads of the conductive pattern of the insulating base, and raising the temperature of the base above the melting point of the metal causing the molten metal to draw back on to the contact pads forming a convex bump. In one embodiment metal bumps are formed on the conductive pattern of the lid of an electronic package and welded through a sealing layer to the ring frame of the package, and through the ring frame connected to the conductive pattern of the base of the package.
1. A method of manufacturing a hermetically sealed electronic package, the electronic package comprising a lid, a frame and a base; the electronic package having a conductive pattern on the lid, the conductive pattern of the lid including at least one component, the conductive pattern of the lid being metallurgically bonded to a conductive pattern of the frame, and the conductive pattern of the frame being metallurgically bonded to a conductive pattern on the base by depositing a metal, having a melting point over 350° C., over portions of a first conductive pattern, melting the metal to form metal bumps or protuberances, and metallurgically bonding the protuberances to a second conductive pattern.
2. A method according to claim 1 wherein the electronic package comprises a lid, a frame and a base, the base and frame being a single unit, and the conductive pattern of the lid is metallurgically bonded to the conductive pattern of the base and frame unit.
3. A method according to claim 1 wherein the metal bumps are metallurgically bonded to the second conductive pattern by a welding process selected from the group consisting of thermocompression, ultrasonic and thermal ultrasonic bonding.
4. A method of manufacturing a hermetically sealed electronic package, the package having three sections: a base, a ring frame joined to the base, the ring frame surrounding an electronic device, and a lid joined to the ring frame, the improvement comprising:
providing the base, ring frame and lid with conductive patterns;
depositing a metal, having a melting point over 350° C., on a selected portion of the conductive pattern of the first section, and melting the metal and cooling the molten metal to form metal bumps;
coating the second section with a sealant which covers metal lands of the conductive pattern;
positioning the first section with the metal bumps opposing the metal lands of the second section;
joining at least two of the sections together by raising the temperature to soften the sealant while raising the pressure and
metallurgically bonding the metal bumps of the first section to the metal lands of the second section thereby joining the conductive pattern of the first section to the conductive pattern of the second section.
5. A method according to claim 4 , wherein the metal of the metal bumps is selected from the group consisting of aluminum, copper, nickel, silver, gold, and alloys comprising these metals.
6. A method of manufacturing an electronic package according to claim 5 , wherein the metal forming the bumps is selected from the group consisting of copper and gold.
7. A method according to claim 4 , wherein the frame and the base are provided as a unit and the frame/base unit is joined to the lid.
8. A method according to claim 4 , wherein the frame and the lid are provided as a unit and the frame/lid unit is joined to the base.
9. A method according to claim 4 , wherein the sealant is glass.
10. A method according to claim 4 wherein the metal bumps of the first section are metallurgically bonded to the metal lands of the second section by a welding process selected from the group consisting of thermocompression, ultrasonic and thermal ultrasonic bonding.
11. A method for manufacturing a “cavity down” electronic package comprising:
providing a base, the base having a conductive pattern with input/output connections for the package, the conductive pattern including conductive vias to metal conductors on the other side which terminate in metal bumps, formed by melting a metal on portion of the conductive pattern, the bumps being comprised of a metal having a melting point over 350° C.;
providing a lid with a conductive pattern and an electronic component attached to the conductive pattern, the conductive pattern terminating in metal bumps formed by melting a metal on portion of the conductive pattern, the bumps being comprised of a metal having a melting point over 350° C.;
providing a frame having a conductive pattern comprising metal lands on its upper and lower surface and conductive vias connecting the lands;
coating the frame with a sealing glass, the sealing glass softening in a temperature range below the melting point of the metal of the metal bumps;
placing the frame, lid and base together with the frame between the lid and the base;
raising the temperature and applying pressure to soften the sealing glass and metallurgically bond the metal bumps lid and the base to the metal lands of the frame, and
cooling to solidify the sealing glass, forming a hermetically sealed electronic package.
12. A method according to claim 11 , wherein the metal of the metal bumps is selected from the group consisting of aluminum, copper, nickel, silver, gold, and alloys comprising these metals.
13. A method according to claim 12 , wherein the metal forming the bumps is selected from the group consisting of copper and gold.
14. A method according to claim 11 wherein the metal bumps of the lid and the base are metallurgically bonded to the metal bumps to the metal lands of the frame by a welding process selected from the group consisting of thermocompression, ultrasonic and thermal ultrasonic bonding.
15. A method for manufacturing an optocoupler comprising:
providing first and second ceramic substrates having conductive patterns;
depositing a metal, having a melting point over 350° C., on selected portions of the conductive patterns of the first and second substrates, and melting the metal to form the metal bumps on the conductive patterns;
mounting a photo emitter on a first one of the ceramic substrates;
mounting a photo detector on a second of the ceramic substrates;
providing a ceramic ring frame, the ring frame having a conductive pattern of metal lands on each side connected by conductive vias;
bonding the first and second ceramic substrates to the ring frame with a sealing glass, and applying sufficient heat and pressure to metallurgically bond the metal bumps on the first and second ceramic substrates to the metal lands of the ring frame.
16. A method according to claim 15 , wherein the metal forming the bumps is selected from the group consisting of copper and gold.
17. A method according to claim 15 wherein the metal bumps are metallurgically bonded to the second conductive pattern by welding process selected from the group consisting of thermocompression, ultrasonic and thermal ultrasonic bonding.
18. A method for manufacturing an optocoupler comprising:
providing a ring frame and a base layer of green ceramics having refractory metal conductive patterns including conductive vias;
joining the frame and base layer together and firing, forming a first single ceramic substrate;
depositing metal lands over the conductive via on the top of the frame;
providing a second ceramic substrate as a lid, the lid having a conductive pattern suitable for mounting a photo-active device, and lands suitable for mating with the metal lands of the frame;
depositing a metal, having a melting point over 350° C., on lands of the conductive patterns of the lid and melting the metal to form the metal bumps on the conductive pattern;
mounting a photo emitter on one of the ceramic substrates;
mounting a photo detector on the other second of the ceramic substrate;
bonding the lid to the ring frame with a sealing glass, and applying sufficient heat and pressure to metallurgically bond the metal bumps on the lid to the metal lands of the ring frame.
19. A method according to claim 18 , wherein the metal forming the lands on the ring frame is selected from the group consisting of copper and gold.
20. A method according to claim 18 , wherein the metal forming the bumps is selected from the group consisting of copper and gold.