Preventing artifacts due to underfill in flip chip imager assembly

Patent metadata

Field	Value
Publication number	US-9503622-B2
Application number	US-201414202256-A
Country	US
Kind code	B2
Filing date	Mar 10, 2014
Priority date	Mar 10, 2014
Publication date	Nov 22, 2016
Grant date	Nov 22, 2016

Abstract

A CMOS imager assembly may include an integrated circuit (IC) having an active-pixel image sensor that is mounted on a printed circuit board (PCB) substrate using flip chip packaging technology. The IC and the PCB may be physically and electrically connected to each other through multiple electrically conductive connectors. An underfill material (which may include an anti-reflective material) may, during assembly, be introduced around the connectors in the space between the IC and the PCB. A chemical or physical discontinuity on the integrated circuit may, during assembly, prevent the underfill material from entering an area framed by the discontinuity, which may include the pixel array of the image sensor. The discontinuity may include a dam-like structure built up on the IC, a trench-like structure created on the IC, or a low surface tension material that has been applied to the surface of the IC.

First claim

What is claimed is:

1. A computer system, comprising:
a printed circuit board;
an integrated circuit device distinct from the printed circuit board, the integrated circuit device comprising an image sensor pixel array;
a plurality of electrically conductive interconnect structures; and
a composite underfill material comprising a polymer and one or more fillers;
wherein the integrated circuit device is coupled to the printed circuit board by the interconnect structures at respective points on the integrated circuit device and the printed circuit board such that the image sensor pixel array faces the printed circuit board;
wherein the composite underfill material envelopes at least a portion of each of the interconnect structures in a space between the integrated circuit device and the printed circuit board; and
wherein a chemical or physical discontinuity situated on the integrated circuit device surrounds the image sensor pixel array and prevents the composite underfill material from extending over the image sensor pixel array.

2. The computer system of claim 1 , wherein the discontinuity comprises metal or metal oxide that forms a dam-type structure on the integrated circuit device.

3. The computer system of claim 1 , wherein the discontinuity comprises a low surface tension material that is built up on the integrated circuit device, forming a chemical discontinuity that prevents the composite underfill material from flowing over the discontinuity.

4. The computer system of claim 1 , wherein the discontinuity comprises a trench on the integrated circuit device.

5. The computer system of claim 1 , wherein the composite underfill material comprises an anti-reflective filler material.

6. The computer system of claim 5 , wherein the anti-reflective filler material comprises carbon black pigment.

7. The computer system of claim 1 , wherein the interconnect structures comprise plated solder bumps.

8. The computer system of claim 1 , wherein the interconnect structures comprise plated copper pillars.

9. The computer system of claim 1 , wherein a width or a diameter of at least one of the interconnect structures is less than 30 μm.

10. An integrated circuit device, comprising:
an image sensor pixel array situated on a particular surface of the integrated circuit device;
a plurality of contact pads for electrically conductive interconnect structures at respective points outside of the image sensor pixel array on the side of the integrated circuit device that comprises the image sensor pixel array;
a chemical or physical discontinuity situated on the particular surface of the integrated circuit device and surrounding the image sensor pixel array between the image sensor array and the plurality of contacts pads and that is configured to prevent an underfill material from extending over the image sensor pixel array during assembly of an imager that includes the integrated circuit device into a flip chip package.

11. The integrated circuit device of claim 10 , wherein the discontinuity comprises metal or metal oxide that forms a dam-type structure on the integrated circuit device.

12. The integrated circuit device of claim 10 , wherein the discontinuity comprises a trench.

13. The integrated circuit device of claim 10 , wherein the discontinuity comprises a low surface tension material that is built up on the integrated circuit device, forming a chemical discontinuity that prevents the underfill material from flowing past the discontinuity.

14. The integrated circuit device of claim 13 , wherein the low surface tension material comprises a chemical vapor deposited polymeric material.

15. The integrated circuit device of claim 10 , wherein the contact pads are configured to form a connection with interconnect structures that comprise solder bumps or copper pillars.

16. The integrated circuit device of claim 10 , wherein the contact pads or interconnect structures comprise gold plating.

17. A method, comprising:
fabricating an integrated circuit device comprising an active image sensor pixel array situated on a particular surface of the integrated circuit device and a plurality of contact pads for respective electrically conductive interconnect structures, wherein the image sensor pixel array is surrounded by a physical or chemical discontinuity situated on the same particular surface of the integrated circuit device as the active image sensor pixel array and between the active image sensor pixel array and the contact pads;
fabricating a printed circuit board distinct from the integrated circuit device, the printed circuit board comprising a plurality of contact pads for the electrically conductive interconnect structures;
mounting the integrated circuit device on the printed circuit board, wherein said mounting comprises:
forming physical and electrically conductive connections between the contact pads on the integrated circuit device and the contact pads on the printed circuit board through the electrically conductive interconnect structures; and
introducing a composite underfill material comprising a polymer and one or more fillers into a space between the integrated circuit device and the printed circuit board in a manner such that the composite underfill material envelopes at least a portion of each of the interconnect structures;

wherein during said mounting, the physical or chemical discontinuity prevents the composite underfill material from extending over the image sensor pixel array.

18. The method of claim 17 , wherein said fabricating the integrated circuit device comprises creating the physical discontinuity by building up metal or metal oxide to form a dam-type structure on the integrated circuit device or by forming a trench in the integrated circuit device.

19. The method of claim 17 , wherein said fabricating the integrated circuit device comprises creating a chemical discontinuity by introducing a low surface tension material on the surface of the integrated circuit device.

20. The method of claim 17 , wherein the composite underfill material comprises an anti-reflective filler material.

Assignees

• Apple Inc

Inventors

• Jiang Tongbi T
• Fan Xiaofeng

Classifications

• H10W90/724

  between a chip and a stacked insulating package substrate, interposer or RDL · CPC title

• H10W72/01308

  using permanent auxiliary members, e.g. using alignment marks · CPC title

• H10W70/681

  comprising holes not having chips therein, e.g. for outgassing, underfilling or bond wire passage · CPC title

• H04N23/57 Primary

  Mechanical or electrical details of cameras or camera modules specially adapted for being embedded in other devices · CPC title

• H04N23/54 Primary

  Mounting of pick-up tubes, electronic image sensors, deviation or focusing coils · CPC title