Structure for repairing or modifying surface connections on circuit boards

• US 7,199,309 B2
• Filed: 06/27/2005
• Issued: 04/03/2007
• Est. Priority Date: 05/10/2001
• Status: Expired due to Fees

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Hoffmeyer, Mark Kenneth, Ma, Wai Mon, Chamberlin, Bruce John, Stack, James R., Nuttall, Arch
• Primary Examiner(s): DINH, TUAN T
• Application Number:
  US11/167,662
• Publication Number:
  US 20050239347A1
• Time in Patent Office: 645 Days
• Field of Search: 174259-266, 361792-795, 29850-853, 439/55
• US Class Current: 174/265
• CPC Class Codes: H05K 1/112 directly combined with via connections
• CPC Class Codes: H05K 2201/1025 Metallic discs small solder preforms other than balls H05K2203/0415
• CPC Class Codes: H05K 2201/10287 Metal wires as connectors or conductors
• CPC Class Codes: H05K 2201/10871 Leads having an integral insert stop
• CPC Class Codes: H05K 2203/0242 Cutting around hole, e.g. for disconnecting land or Plated Through-Hole [PTH] or for partly removing a PTH
• CPC Class Codes: H05K 2203/175 Configurations of connections suitable for easy deletion, e.g. modifiable circuits or temporary conductors for electroplating; Processes for deleting connections
• CPC Class Codes: H05K 3/225 Correcting or repairing of printed circuits H05K1/0292, H05K3/222, H05K3/288, H05K3/4685 take precedence
• CPC Class Codes: H05K 3/4046 using auxiliary conductive elements, e.g. metallic spheres, eyelets, pieces of wire
• CPC Class Codes: H05K 3/429 Plated through-holes specially for multilayer circuits, e.g. having connections to inner circuit layers
• CPC Class Codes: Y10T 29/49165 by forming conductive walled aperture in base
• CPC Class Codes: Y10T 29/49167 with deforming of conductive path

Abstract

A method to replace an electrical interface on a printed circuit board having a plurality of contact pads on a top surface, the contact pads being connected to conducting material extending through said circuit board. For the contact pad being replaced, drilling a hole through said printed circuit board at that location, and removing any remaining conductor material attached to the contact pad on the top board surface. Providing a replacement conductor/contact pad structure having a generally T-configuration with a stem and a head that completely surrounds the stem, wherein said head has a diameter greater than the diameter of the drilled hole. Inserting the replacement conductor/contact pad into the hole with said stem extending beyond the second surface of the board with the bottom surface of the head being in contact with the first surface of said board. A replacement conductor/contact pad on repaired board is also described.

Claims

1. A replacement conductor/contact pad structure of a land grid array to repair or modify a printed circuit board containing a plurality of contact pads, said replacement conductor/contact pad structure being T-shaped and having a flat head portion and a stem and wherein said stem is completely surrounded by said head portion, and wherein said stem is longer than the thickness of the circuit board, said stem being surrounded adjacent said head by a dielectric material extending in contact with said stem less than the length of the stem portion, and wherein the flat surface of said head a coating thereon selected from the group of gold, nickel, palladium, and nickel/palladium alloy.

2. The structure as defined in claim 1 wherein said dielectric material surrounding said stem extends from said head a distance no more than the thickness of the board on which the replacement conductor/contact pad structure is to be used.

3. The structure as defined in claim 1 wherein the thickness of the head is substantially the same thickness of the contact pads of the land grid array.

4. The structure as defined in claim 1 wherein said head is thicker than the thickness of the contact pads on the circuit board to be refinished.

5. The invention as defined in claim 1 wherein said first surface of said circuit board includes a counterbore around said hole and in which counterbore the head of said conductor/contact pad is disposed.

11. The invention as defined in claim 1 wherein said head portion of said conductor/contact pad is adhesively bonded to said circuit board when in place.

6. A printed circuit board comprising at least one layer of dielectric material and having a first surface and a second surface, and having a plurality of contact pads mounted on a first surface thereof, and wherein at least one of said contact pads is connected by a connector to at least one electrical component mounted on at least one of the layers of dielectric material by a plated through hole or via, and wherein said plated through hole has been modified by drilling an opening between said first surface and said second surface having a diameter sufficient to electrically isolate a corresponding one of the contact pads from said electrical component, a preformed replacement conductor/contact pad structure disposed in said opening, said preformed contact pad structure having a flat head and a stem, said head having a diameter larger than the diameter of the hole and said stem extending beyond the second surface of the printed circuit board, and a contact surface of said head portion being in contact with the first surface of said printed circuit board, and wherein the flat surface of said head has a coating thereon selected from the group of gold, nickel, palladium, and nickel/palladium alloy.

7. The printed circuit board as defined in claim 6 wherein said contact surface of said conductor/contact pad which contacts the first surface of the circuit board is adhesively bonded to said first surface of said printed circuit board.

8. The printed circuit board as defined in claim 6 wherein said stem of said conductor/contact pad has secured thereto a dielectric material disposed in said opening and extending no more than the thickness of the printed circuit board wherein said stem extends beyond said dielectric material.

9. The printed circuit board as defined in claim 6 wherein said head and said stem are substantially circular in cross-section.

10. A printed circuit board comprising at least one layer of dielectric material and having a first surface and a second surface, and having a plurality of contact pads mounted on a first surface thereof, and wherein at least one of said contact pads is connected by a connector to at least one electrical component mounted on at least one of the layers of dielectric material by a plated through hole or via, and wherein said plated through hole has been modified by drilling an opening between said first surface and said second surface having a diameter sufficient to electrically isolate a corresponding one of the contact pads from said electrical component, a preformed replacement conductor/contact pad structure disposed in said opening, said preformed contact pad structure having a flat head and a stem, said head having a diameter larger than the diameter of the hole and said stem extending beyond the second surface of the printed circuit board, and wherein said first surface of said circuit board includes a counterbore around said hole and in which the head of said conductor/contact pad is disposed, and wherein the flat surface of said head has a coating thereon selected from the group of gold, nickel, palladium, and nickel/palladium alloy.