Determination of quality of bonding between a conductive ball and a conductive pad within an IC package

• US 6,193,134 B1
• Filed: 06/26/2000
• Issued: 02/27/2001
• Est. Priority Date: 06/26/2000
• Status: Expired due to Fees

• Current Assignee: Advanced Micro Devices, Inc.
• Original Assignee: Advanced Micro Devices, Inc.
• Inventors: Vijchulata, Prakorn, Sabyeying, Watana
• Primary Examiner(s): Shaw, Clifford C.
• Assistant Examiner(s): DUNN, COLLEEN P
• Application Number:
  US09/602,733
• Time in Patent Office: 246 Days
• Field of Search: 228/103, 228/105, 228/178, 228/179.1, 228/180.21, 228/180.22, 228/180.1
• US Class Current: 228/103
• CPC Class Codes: B23K 2101/38 Conductors
• CPC Class Codes: B23K 31/12 relating to investigating the properties, e.g. the weldability, of materials

Abstract

The quality of bonding between a conductive ball and a conductive pad of a lead frame strip of an IC package are determined by etching the conductive ball from the conductive pad, and analyzing the bottom view of the conductive ball. The conductive ball is comprised of a first conductive material and a conductive pad is comprised of a second conductive material. The conductive ball is bonded to the conductive pad by formation of an intermediary material formed from the first conductive material of the conductive ball and the second conductive material of the conductive pad. The lead frame strip is immersed within an etching solution such that the intermediary material is etched between the conductive ball and the conductive pad until the conductive ball may be decoupled from the conductive pad. The conductive ball has a first color in areas where the intermediary material was not abutting the conductive ball and has a second color in areas where the intermediary material was abutting the conductive ball when the conductive ball was bonded to the conductive pad. The intermediary material was abutting an intermediary material area of the conductive ball when the conductive ball was bonded to the conductive pad. A magnified image of the intermediary material area on the conductive ball is captured by a microscope with the intermediary material area being substantially centered within the magnified image while the conductive ball is decoupled from the conductive pad. The magnified image of the intermediary material area on the conductive ball is analyzed by a data processor to determine quality of bonding between the conductive ball and the conductive pad.

Claims

1. A method for determining quality of bonding between a conductive ball comprised of a first conductive material and a conductive pad comprised of a second conductive material, said conductive ball being bonded to said conductive pad by formation of an intermediary material formed from said first conductive material of said conductive ball and said second conductive material of said conductive pad, the method including the steps of:

A. etching said intermediary material between said conductive ball and said conductive pad such that said conductive ball is decoupled from said conductive pad, said conductive ball having a first color in areas where said intermediary material was not abutting said conductive ball and having a second color in areas where said intermediary material was abutting said conductive ball when said conductive ball was bonded to said conductive pad;

and wherein said intermediary material was abutting an intermediary material area of said conductive ball when said conductive ball was bonded to said conductive pad;

B. capturing a magnified image of said intermediary material area on said conductive ball with said intermediary material area being substantially centered within said magnified image while said conductive ball is decoupled from said conductive pad;

and wherein said intermediary material area appears as said second color within said magnified image and wherein an area of said conductive ball wherein said intermediary material was not abutting said conductive ball appears as said first color within said magnified image; and

C. analyzing said magnified image of said intermediary material area on said conductive ball to determine quality of bonding between said conductive ball and said conductive pad.

2. The method of claim 1, wherein said etching of said intermediary material in said step A further includes the step of:

immersing said conductive ball and said conductive pad bonded by said intermediary material in an etching solution comprised of about 30% (weight/volume) sodium hydroxide (NaOH) at a temperature of about 80°

Celsius for a time period of about 1 minute.

3. The method of claim 1, wherein said step of analyzing said magnified image in said step C includes calculating a percentage of said intermediary material area to a total area of said conductive ball within said magnified image to determine quantity of bonding between said conductive ball and said conductive pad.

4. The method of claim 1, wherein said conductive ball is coupled via a wire to a lead frame strip of an IC (integrated circuit) package, and wherein said conductive pad is disposed on an IC (integrated circuit) die supported by a die frame dap, the method further including the step of:

cutting said die frame dap with said IC die thereon away from said lead frame strip after said step A and before said step B such that said conductive ball is floating via said wire that is coupled to said lead frame strip.

5. The method of claim 1, wherein said conductive ball is comprised of gold (Au).

6. The method of claim 5, wherein said conductive pad is comprised of aluminum (Al), and wherein said intermediary material is comprised of a gold and aluminum alloy (Au_xAl_y).

7. A method for determining quality of bonding between a gold ball and an aluminum pad, said gold ball being bonded to said aluminum pad by formation of an intermetallic alloy formed from gold of said gold ball and aluminum of said aluminum pad, the method including the steps of:

A. etching said intermetallic alloy between said gold ball and said aluminum pad such that said gold ball is decoupled from said aluminum pad, said gold ball having a gold color in areas where said intermetallic alloy was not abutting said gold ball and having a gray color in areas where said intermetallic alloy was abutting said gold ball when said gold ball was bonded to said aluminum pad, wherein said step A further includes the step of;

immersing said gold ball and said aluminum pad bonded by said intermetallic alloy in an etching solution comprised of about 30% (weight/volume) sodium hydroxide (NaOH) at a temperature of about 80°

Celsius for a time period of about 1 minute;

and wherein said intermetallic alloy was abutting said gold ball on an intermetallic area of said gold ball when said gold ball was bonded to said aluminum pad;

and wherein said gold ball is coupled via a wire to a lead frame strip of an IC (integrated circuit) package, and wherein said aluminum pad is disposed on an IC (integrated circuit) die supported by a die frame dap;

B. cutting said die frame dap with said IC die thereon away from said lead frame strip such that said gold ball is floating via said wire that is coupled to said lead frame strip;

C. capturing a magnified image of said intermetallic area on said gold ball with said intermetallic area being substantially centered within said magnified image while said gold ball is decoupled from said aluminum pad;

and wherein said intermetallic area appears as said gray color within said magnified image and wherein an area of said gold ball wherein said intermetallic alloy was not abutting said gold ball appears as said gold color within said magnified image; and

D. analyzing said magnified image of said intermetallic alloy on said gold ball by calculating a percentage of said intermetallic area to a total area of said gold ball within said magnified image to determine quantity of bonding between said gold ball and said aluminum pad.