Method for determining degree of interconnection of solder joints using X-ray inspection

• US 5,012,502 A
• Filed: 06/18/1990
• Issued: 04/30/1991
• Est. Priority Date: 06/18/1990
• Status: Expired due to Fees

• Current Assignee: ThermoSpectra Corp (Thermo Fisher Scientific Incorporated)
• Original Assignee: IRT Corporation (William M. Scranton)
• Inventors: Battin, John, Stroebel, Thomas
• Primary Examiner(s): Westin, Edward P.
• Assistant Examiner(s): CHU, KIM KWOK
• Application Number:
  US07/539,132
• Time in Patent Office: 316 Days
• Field of Search: 378/58, 378/99, 228/103, 228/104
• US Class Current: 378/58
• CPC Class Codes: B23K 31/12 relating to investigating the properties, e.g. the weldability, of materials
• CPC Class Codes: H05K 1/0269 for visual or optical inspection
• CPC Class Codes: H05K 1/111 Pads for surface mounting, e.g. lay-out
• CPC Class Codes: H05K 2201/09427 Special relation between the location or dimension of a pad or land and the location or dimension of a terminal
• CPC Class Codes: H05K 2203/162 Testing a finished product, e.g. heat cycle testing of solder joints patterns for electrical inspection or testing H05K1/0268
• CPC Class Codes: H05K 3/3436 having an array of bottom contacts, e.g. pad grid array or ball grid array components
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

Determination of the quality of blind solder interconnections by X-ray inspection is made possible by forming indicator features on the pads of a component and the pads of the surface on which the component is to be mounted. The indicator features consist of an area which is different in size and/or shape than that of the other pad to be joined. For example, the indicator feature may be a circular region with an area approximately twice that of the pad to which it is to be joined. A relatively large amount of solder is deposited on the smaller pad and the two pads are placed in contact. During reflow, the molten solder on the smaller pad will flow to cover the full area of the indicator feature, indicating that a good interconnection was obtained. The indicator features may also be a different shape from that of the pad to which it is to be joined so that the solder deposited on the pad will take on the shape of the indicator feature when successful interconnection is achieved.

Claims

1. A method of determining the quality of solder interconnection of a solder joint between a first electrical member and a second electrical member by X-ray inspection comprising:

forming a first indicator feature at a first solder joint location of said first electrical member, said first indicator feature having a first set of parameters comprising size, shape and orientation;

forming a second indicator feature at a second solder joint location of said second electrical member, said second indicator feature having a second set of parameters comprising size, shape and orientation of which at least one of said second set of parameters is different from that of said first set of parameters, so that at least one edge of both said first and said second indicator features are visible in an X-ray image of said solder joint, and so that melting of solder deposited on said first indicator feature when said solder is in contact with said second indicator feature will cause said solder to flow and solidify upon cooling to cover all of said first indicator feature and all of said second indicator feature; and

taking an X-ray image of said solder joint;

inspecting said X-ray image to determine whether said solder has fully covered said first indicator feature and said second indicator feature, whereby quality of said solder joint interconnection is determined to be good if said solder flowed to fully cover both indicator features, and quality of said solder joint interconnection being determined to be poor if said solder did not flow to fully cover both indicator features.

2. A method as in claim 1 wherein said X-ray image is digitized by a digital computer, and inspection is performed thereby.

3. A method as in claim 1 wherein said first electrical member is a printed circuit board and said second electrical member is an electronic component.

4. A method as in claim 1 wherein said first electrical member is an electronic component and said second electrical member is a printed circuit board.

5. A method as in claim 1 wherein said first electrical member is a hybrid board assembly and said second electrical member is an electrical component.

6. A method as in claim 1 wherein said first electrical member is an electronic component and said second electrical member is a hybrid board assembly.

7. A method as in claim 1 wherein said first electrical member is a package for semiconductors and said second electrical member is a semiconductor chip.

8. A method as in claim 1 wherein said first electrical member is a semiconductor chip and said second electrical member is a package for semiconductors.

9. A method of determining the quality of solder interconnection of a solder joint between a first electrical member and a second electrical member by X-ray inspection, comprising:

forming an indicator feature at a solder joint location of said second electrical member, said indicator feature having a first set of parameters comprising area, shape and orientation which are different from a second set of parameters of a connection pad on said first electrical member, so that edges of said indicator feature are visible in an X-ray image of said solder joint, and so that melting of solder deposited on said connection pad, when said solder is in contact with both said indicator feature and said connection pad, will cause said solder to flow and solidify upon cooling to cover said indicator feature;

taking an X-ray image of said solder joint showing said indicator feature; and

inspecting said X-ray image to determine whether said solder has flowed fully to cover said indicator feature, quality of said solder interconnection being determined to be good if said solder fully covered said indicator feature, and quality of said solder interconnection being determined to be poor if said solder did not fully cover said indicator feature.

10. A method as in claim 9 wherein said X-ray image is digitized by a digital computer and inspection is performed thereby.

11. A method as in claim 9 wherein said first electrical member is a printed circuit board and said second electrical member is an electronic component.

12. A method as in claim 9 wherein said first electrical member is an electronic component and said second electrical member is a printed circuit board.

13. A method as in claim 9 wherein said first electrical member is a hybrid board assembly and said second electrical member is an electrical component.

14. A method as in claim 9 wherein said first electrical member is an electronic component and said second electrical member is a hybrid board assembly.

15. A method as in claim 9 wherein said first electrical member is a package for semiconductors and said second electrical member is a semiconductor chip.

16. A method as in claim 9 wherein said first electrical member is a semiconductor chip and said second electrical member is a package for semiconductors.

17. A method of determining the quality of solder interconnection between a double-sided first electrical member and at least two different electrical members by X-ray inspection comprising:

forming a first indicator feature at a first solder joint location on a first side of said first electrical member, said first indicator feature having a first set of parameters comprising shape, orientation and area, at least one of said first set of parameters being different than a second set of parameters of a corresponding pad of a second electrical member so that heat treatment of solder deposited on said corresponding pad of said second electrical member when said solder is in contact with said first indicator feature causes said solder to flow and solidify upon cooling to cover said first indicator feature;

forming a second indicator feature at a second solder joint location on a second side of said first electrical member opposite said first side, said second indicator feature having a third set of parameters comprising shape, orientation and area, at least one of said set third set of parameters being different from one of said first set of parameters, said area of said third set of parameters being different than an area of a corresponding pad of a third electrical member, so that heat treatment of solder deposited on said corresponding pad of said third electrical member causes solder to flow and solidify upon cooling to cover said second indicator feature, said second indicator feature being disposed opposite said first indicator feature so as to be overlying said first indicator feature with at least one edge of each indicator feature visible when viewed by X-ray inspection;

taking an X-ray image of both said solder joints showing both said first and second indicator features; and

inspecting said X-ray image to determine whether said solder has flowed fully to cover said first indicator feature and said second indicator feature, quality of solder interconnection on said first side being determined to be good if said solder flowed to fully cover said first indicator feature, and quality of said solder joint interconnection on said first side being determined to be poor if said solder did not fully cover said first indicator feature, and quality of solder interconnection on said second side being determined to be good if said solder flowed to the edges of said second indicator feature, and quality of said solder joint interconnection on said second side being determined to be poor if said solder did not fully cover said second indicator feature.

18. A method as in claim 17 wherein said X-ray image is digitized by a digital computer and inspection is performed thereby.

19. A method as in claim 17 wherein said first electrical member is a printed circuit board and said second electrical member is an electronic component.

20. A method as in claim 17 wherein said first electrical member is an electronic component and said second electrical member is a printed circuit board.

21. A method as in claim 17 wherein said first electrical member is a hybrid board assembly and said second electrical member is an electrical component.

22. A method as in claim 17 wherein said first electrical member is an electronic component and said second electrical member is a hybrid board assembly.

23. A method as in claim 17 wherein said first electrical member is a package for semiconductors and said second electrical member is a semiconductor chip.

24. A method as in claim 17 wherein said first electrical member is a semiconductor chip and said second electrical member is a package for semiconductors.

25. A method of determining the quality of solder interconnection between said first electrical member and a second electrical member by X-ray inspection comprising:

forming an indicator feature at a solder joint location of said first electrical member, said indicator feature having a first shape and first area which is different from a second area of a corresponding pad of said second electrical member, said corresponding pad having a second shape, so that melting of solder deposited on said corresponding pad when said solder is in contact with said indicator feature causes said solder to flow and solidify upon cooling to cover said first area;

taking an X-ray image of said solder joint showing said indicator feature; and

inspecting said X-ray image to determine whether said solder has flowed fully to cover said indicator feature, quality of said solder interconnection being determined to be good if said solder fully covered said indicator feature, and quality of said solder interconnection being determined to be poor if said solder did not fully cover said indicator feature.

26. A method as in claim 25 wherein said first shape is the same as said second shape.

27. A method as in claim 25 wherein said first area is at least twice as large as said second area.