Method of making an electronic assembly

• US 20070023488A1
• Filed: 07/26/2005
• Published: 02/01/2007
• Est. Priority Date: 07/26/2005
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Delphi Technologies, Inc. (Aptiv PLC)
• Inventors: Laudick, David, Lawlyes, Daniel
• Granted Patent: US 7,510,108 B2
• Time in Patent Office: Days
• US Class Current: 228/180.220
• CPC Class Codes: H01L 21/563 Encapsulation of active face of flip-chip device, e.g. underfilling or underencapsulation of flip-chip, encapsulation preform on chip or mounting substrate
• CPC Class Codes: H01L 21/565 Moulds
• CPC Class Codes: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/32225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/73203 Bump and layer connectors
• CPC Class Codes: H01L 2224/73204 the bump connector being embedded into the layer connector
• CPC Class Codes: H01L 2224/73253 Bump and layer connectors
• CPC Class Codes: H01L 2224/83102 using surface energy, e.g. capillary forces
• CPC Class Codes: H01L 2224/92125 the second connecting process involving a layer connector
• CPC Class Codes: H01L 24/28 Structure, shape, material or disposition of the layer connectors prior to the connecting process
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/01029 Copper [Cu]
• CPC Class Codes: H01L 2924/01082 Lead [Pb]
• CPC Class Codes: H01L 2924/14 Integrated circuits

Abstract

A method of making an electronic assembly comprising an electronic component that is attached to a circuit board by protruding solder bumps of the electronic component places the electronic component on a surface of the circuit board so that solder bumps on the bottom of the electronic component engage contact pads on the top of the circuit board. The solder bumps are then reflowed to attach the electronic component to the circuit board after which the electronic component is underfilled by providing a mold die having a mold cavity, a gate leading into the mold cavity and a vent leading out of the mold cavity. The mold die is placed over the electronic component and onto the surface of the circuit board so that the electronic component is inside the mold cavity and the mold cavity is sealed. An encapsulating material, preferably an epoxy material, is transferred or injected into the mold cavity to fill space between the respective surfaces of the electronic component and the circuit board and then cured to encapsulate the solder bumps that have been reflowed. An optional integrated heat sink for the electronic component may be used when practicing the method of the invention to make an electronic assembly.

Claims

1. A method of making an electronic assembly comprising an electronic component that is attached to a circuit board by protruding solder bumps of the electronic component comprising the steps of:

placing the electronic component on a surface of the circuit board so that the solder bumps of the electronic component engage contact pads in electrical contact with traces of the circuit board,

reflowing the solder bumps to attach the electronic component to the circuit board, and

underfilling the electronic component, the underfilling comprising the steps of

providing a mold die having a mold cavity, a gate leading into the mold cavity and a vent leading out of the mold cavity,

placing the mold die over the electronic component and onto the surface of the circuit board so that the electronic component is inside the mold cavity and the mold cavity is sealed, and

transferring or injecting an epoxy material into the mold cavity to fill space between the respective surfaces of the electronic component and the circuit board and encapsulate the solder bumps that have been reflowed.

2. The method of making the electronic assembly of claim 1 wherein the electronic component is a flip chip.

3. The method of making the electronic assembly of claim 1 wherein the electronic component is a packaged integrated circuit that includes a housing shell and a board component that has solder bumps.

4. The method of making the electronic assembly of claim 1 wherein a heat sink is placed over the electronic component before underfilling the electronic component, the heat sink being inside the mold cavity after the mold die is placed over the electronic component.

5. The method of making the electronic assembly of claim 2 wherein the flip chip has a peripheral surface that is exposed in the mold cavity so that the peripheral surface is encapsulated when the epoxy material is transferred or injected into the mold cavity.

6. The method of making the electronic assembly of claim 2 wherein the mold die is removed and the electronic assembly is trimmed to remove any epoxy runners that were in the gate and the vent.

7. The method of making the electronic assembly of claim 3 wherein the flip chip is attached to a heat sink with an intervening thermal interposer.

9. The method of making the electronic assembly of claim 5 wherein the heat sink shell has a peripheral wall engaging the laminated circuit board and wherein the peripheral wall of the heat sink shell has flow windows extending through the peripheral wall for epoxy to pass through and into the space between the respective surfaces of the flip chip and the laminated circuit board.

10. The method of making the electronic assembly of claim 6 wherein the flip chip has a peripheral surface that is exposed in the mold cavity so that the peripheral surface is encapsulated when the epoxy material is injected into the mold cavity.

11. The method of making the electronic assembly of claim 6 wherein the mold die is removed and the electronic assembly is trimmed to remove any epoxy runners from the gate and the vent.

8. A method of making an electronic assembly having a laminated circuit board with contact pads on a surface and a flip chip having protruding solder bump on a surface comprising the steps of:

placing the flip chip on the surface of the laminated circuit board so that the solder bumps of the flip chip engage the contact pads of the laminated circuit device,

providing a heat sink shell,

placing the heat sink shell over the flip chip and onto the surface of the laminated circuit board,

providing a mold die having a mold cavity, a gate leading into the mold cavity and a vent leading out of the mold cavity,

placing the mold die over the heat sink shell and onto the surface of the laminated circuit device outwardly of the flip chip so that the flip chip and the heat sink are in the mold cavity and the mold cavity is sealed, and

injecting an epoxy material into the mold cavity to fill space between the respective surfaces of the flip chip and the laminated circuit board and encapsulate the solder bumps and contacts.