Method for making and testing thermocompression bonds

• US 6,520,026 B1
• Filed: 11/03/1999
• Issued: 02/18/2003
• Est. Priority Date: 11/03/1999
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Anderson, Lynda L., Waddell, Kent D., Mahoney, Robert E. Jr., Granier, Gilles, Moore, Bruce E., Scea, Kenneth A.
• Primary Examiner(s): Noori, Max
• Assistant Examiner(s): Martir, Lilybett
• Application Number:
  US09/433,027
• Time in Patent Office: 1,203 Days
• Field of Search: 738/27, 738/28, 738/30, 738/34, 738/35
• US Class Current: 73/827
• CPC Class Codes: B23K 20/004 Wire welding
• CPC Class Codes: B23K 2101/38 Conductors
• CPC Class Codes: G01N 19/04 Measuring adhesive force between materials, e.g. of sealing tape, of coating
• CPC Class Codes: G01N 2203/0091 Peeling or tearing
• CPC Class Codes: G01N 3/00 Investigating strength properties of solid materials by application of mechanical stress
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/45147 Copper (Cu) as principal constituent
• CPC Class Codes: H01L 2224/4847 the connecting portion on the bonding area of the semiconductor or solid-state body being a wedge bond
• CPC Class Codes: H01L 2224/78 Apparatus for connecting with wire connectors
• CPC Class Codes: H01L 2224/85 using a wire connector
• CPC Class Codes: H01L 2224/85203 Thermocompression bonding
• CPC Class Codes: H01L 24/45 of an individual wire connector
• CPC Class Codes: H01L 24/48 of an individual wire connector
• CPC Class Codes: H01L 24/78 Apparatus for connecting with wire connectors
• CPC Class Codes: H01L 24/85 using a wire connector wire bonding in general B23K20/004
• 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 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/01005 Boron [B]
• CPC Class Codes: H01L 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01029 Copper [Cu]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/19041 : being a capacitor

Abstract

A method for making and testing the thermal compression bond between a wire and a contact or terminal lead of a connector wherein the wire and contact/terminal lead are positioned between opposing electrodes, and a direct current is passed through the electrodes, wire and contact/terminal lead to make a direct attach thermocompression bond. Sample bonds are subjected to a peel test to determine if the thermocompression bonds are within specification. The peel test includes securing the contact/terminal lead, bend the wire 90 degrees from the contact/terminal lead, and applying force to the wire at a constant rate of pull until thermocompression bond is broken and the wire is separated from the contact/terminal lead. The peel force required to break the bond is then compared to a standard to determine if the thermocompression bonds are within determined specifications. Additionally, an axial pull test may also be performed.

Claims

1. A method for testing an assembly process for making direct attachment of wires to contact/terminal leads, the method comprising the following steps:

(a) aligning a wire and a contact/terminal lead between a pair of opposed electrodes such that the boundary of a portion of the wire is contained within the boundary of a portion of the contact/terminal lead, one electrode being centered on the wire portion such that there is undisturbed wire extending from both sides of said electrode;

(b) applying force through the electrodes to the wire and the contact/terminal lead such that the wire is deformed;

(c) passing electrical current through the electrodes, wire and contact/terminal lead to make a thermocompression bond of the wire to the contact/terminal lead;

(d) repeating steps a-c thereby producing at least one set of attached wires and contact/terminal leads;

(e) performing a peel test on a subgroup of each set produced in step (d);

thereby determining if the thermocompression bonds of the attached wires and contact/terminal leads produced in step (d) are acceptable.

2. The method of claim 1 wherein the deformation of step (b) is less that 50% of the outside diameter of the wire.

3. The method of claim 1 wherein the peel test comprises:

securing the contact/terminal lead;

bending the wire 90 degrees from the contact/terminal lead;

pulling the wire with a constant rate of pull until the thermocompression bonds between the wire and the contact/terminal lead breaks; and

comparing the peel force required to break the thermocompression bond to a standard.

4. The method of claim 3 wherein said constant rate of pull is 50 mm per minute.

5. The method of claim 3 wherein said standard is not less than 50% of the wire tensile strength with a minimum capability index (C_pk) of 1.5, wherein the C_pk is calculated as follows:

6. The method of claim 5 wherein said lower specification limit for annealed copper wire is according to the following table for the specified wire sizes:

7. The method of claim 3 wherein a lower control limit average peel force (LCL X^bar) is established, and an upper control limit average peel force (UCL X^bar) is established, and the comparing step includes determining that the peel force is between the LCL X^bar and the UCL X^bar values.

8. The method of claim 3 wherein a lower control limit range value (LCL R^bar) is established, and an upper control limit range value (UCL R^bar) is established, wherein the range is the difference between the maximum peel force measured and the minimum peel force measured for the subgroup of peel tests, and the comparing step includes determining that the peel force is between the LCL R^bar and the UCL R^bar values.

9. The method of claim 1 including after step (e) the step of:

(f) performing an axial pull test of a subgroup of each set produced in step (d).

10. The method of claim 9 wherein the axial pull test comprises:

securing the contact/terminal lead;

axially pulling the wire with a constant rate of pull until the thermocompression bond between the wire and the contact/terminal lead breaks; and

comparing the axial pull force required to break the thermocompression bond to a standard.

11. The method of claim 10 wherein said constant rate of pull is 50 mm per minute.

12. The method of claim 10 wherein said standard is not less than 50% of the wire tensile strength with a minimum capability index (C_pk) of 1.5, wherein the C_pk is calculated as follows:

13. The method of claim 12 wherein said lower specification limit for annealed copper wire is according to the following table for the specified wire sizes:

14. The method of claim 11 wherein a lower control limit average peel force (LCL X^bar) is established, and an upper control limit average axial pull force (UCL X^bar) is established, and the comparing step includes determining that the axial pull force is between the LCL X^bar and the UCL X^bar values.

15. The method of claim 11 wherein a lower control limit range value (LCL R^bar) is established, and an upper control limit range value (UCL R^bar) is established, wherein the range is the difference between the maximum axial pull force measured and the minimum axial pull force measured for the subgroup of axial pull tests, and the comparing step includes determining that the axial pull force is between the LCL R^bar and the UCL R^bar values.

16. A method of testing thermocompression bonds of wires to contact/terminal leads from at least one set of direct attachments, said method comprising:

securing each contact/terminal lead of a subgroup of the contact/terminal leads from each set;

bending the wires of the subgroup 90 degrees from the secured contact/terminal leads;

pulling the wires with a constant rate of pull until the thermocompression bonds between the wire and the contact/terminal lead breaks; and

comparing the peel force required to break the thermocompression bonds to a statistically derived standard;

wherein a lower control limit average peel force (LCL X^bar) is established, and an upper control limit average peel force (UCL X^bar) is established, and the comparing step includes determining that the peel force is between the LCL X^bar and the UCL X^bar values.

17. The method of claim 16 wherein said constant rate of pull is 50 mm per minute.

18. The method of claim 16 wherein said standard is not less than 50% of the wire tensile a minimum capability index (C_pk) of 1.5, wherein the C_pk is calculated as follows:

19. The method of claim 18 wherein said lower specification limit for annealed copper wire is according to the following table for the specified wire sizes:

20. A method of testing thermocompression bonds of wires to contact/terminal leads from at least one set of direct attachments, said method comprising:

securing each contact/terminal lead of a subgroup of the contact/terminal leads from each set;

bending the wires of the subgroup 90 degrees from the secured contact/terminal leads;

pulling the wires with a constant rate of pull until the thermocompression bonds between the wire and the contact/terminal lead breaks; and

comparing the peel force required to break the thermocompression bonds to a statistically derived standard;

wherein a lower control limit range value (LCL R^bar) is established, and an upper control limit range value (UCL R^bar) is established, wherein the range is the difference between the maximum peel force measured and the minimum peel force measured for the subgroup of peel tests, and the comparing step includes determining that the peel force is between the LCL R^bar and the UCL R^bar values.

21. A method of testing thermocompression bonds of wires to contact/terminal leads from at least one set of direct attachments, said method comprising:

securing each contact/terminal lead of a subgroup of the contact/terminal leads from each set;

axially pulling the wires with a constant rate of pull until the thermocompression bonds between the wire and the contact/terminal lead breaks; and

comparing the axial pull force required to break the thermocompression bonds to a statistically derived standard;

wherein a lower control limit average peel force (LCL X^bar) is established, and an upper control limit average axial pull force (UCL X^bar) is established, and the comparing step includes determining that the axial pull force is between the LCL X^bar and the UCL X^bar values.

22. The method of claim 21 wherein said constant rate of pull is 50 mm per minute.

23. The method of claim 21 wherein said standard is not less than 50% of the wire tensile strength with a minimum capability index (C_pk) of 1.5, wherein the C_pk is calculated as follows:

24. The method of claim 21, wherein said lower specification limit for annealed copper wire is according to the following table for the specified wire sizes:

25. A method of testing thermocompression bonds of wires to contact/terminal leads from at least one set of direct attachments, said method comprising:

securing each contact/terminal lead of a subgroup of the contact/terminal leads from each set;

axially pulling the wires with a constant rate of pull until the thermocompression bonds between the wire and the contact/terminal lead breaks; and

comparing the axial pull force required to break the thermocompression bonds to a statistically derived standard;

wherein a lower control limit range value (LCL R^bar) is established, and an upper control limit range value (UCL R^bar) is established, wherein the range is the difference between the maximum axial pull force measured and the minimum axial pull force measured for the subgroup of axial pull tests, and the comparing step includes determining that the axial pull force is between the LCL R^bar and the UCL R^bar values.