Substrate plating methods and apparatus
An apparatus includes a first package substrate, a second package substrate, and a deformable conductor sandwiched between the first package substrate and the second package substrate.
The inventive subject matter is related to plating of a substrate. More specifically, embodiments of the invention relate to methods and apparatus for plating a substrate without the need of a plating bar.
BACKGROUND INFORMATIONIntegrated circuits have been manufactured for many years. Manufacturing integrated circuits involves integrating various active and passive circuit elements into a piece of semiconductor material, referred to as a die. The die is attached to a package substrate to form a ceramic or plastic package. In some embodiments, the die is encapsulated within the package substrate to form or finish the package. The finished package can be attached directly to a printed circuit board by connecting input/output pins, arranged along a major surface of the package, to corresponding pads on the printed circuit board. In other embodiments, the finished package is attached to an interposer. The finished package and the interposer are then attached to a printed circuit board. An electronic system can be formed by connecting various finished packages, containing various dies or integrated circuits, to a printed circuit board. The printed circuit board will include traces for interconnecting the various integrated circuits or dies associated with the various packages.
Advances in semiconductor manufacturing technology have resulted in increased numbers of transistors on each integrated circuit, and an increase in the functionality of each integrated circuit. One result of the increase in functionality includes an increase in the number of input/output (I/O) connections between the integrated circuit and the package substrate. One adaptation designed to address the increased need for I/O connections without consuming an unacceptably large amount of area was the development of ball grid array (BGA) I/O connections for an integrated circuit. BGA devices include a plurality of solder bumps formed by a process commonly referred to as controlled collapsed chip connection (C4). In such a package, a large number of I/O connection terminals are disposed in a two dimensional array over a substantial portion of a major surface of the package. In some instances, BGA packages are directly attached to a supporting substrate such as a printed circuit board. In other instances, an interposer is directly attached to the printed circuit board and the BGA package is attached to the interposer. The interposer includes routing traces and vias that connect the solder bumps of the BGA to contacts that are attached to the printed circuit board. The interposer “fans out” the relatively small die pad pitch of the integrated circuit to the larger contact pad pitch of the printed circuit board. In many applications, the interposer material has a coefficient of thermal expansion intermediate the coefficient of thermal expansion of the printed circuit board and the coefficient of thermal expansion of the BGA package. The interposer, therefore, reduces mechanical stress induced by different coefficients of thermal expansion between the package and the printed circuit board.
BRIEF DESCRIPTION OF THE DRAWINGSEmbodiments of the invention are pointed out with particularity in the appended claims. However, a more complete understanding of the inventive subject matter may be derived by referring to the detailed description when considered in connection with the figures, wherein like reference numbers refer to similar items throughout the figures, and:
The description set out herein illustrates various embodiments of the invention, and such description is not intended to be construed as limiting in any manner.
DETAILED DESCRIPTIONIn the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the inventive subject matter can be practiced. The embodiments illustrated are described in sufficient detail to enable those skilled in the art to practice the teachings disclosed herein. Other embodiments can be utilized and derived therefrom, such that structural and logical substitutions and changes can be made without departing from the scope of the inventive subject matter. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of various embodiments of the invention is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled.
The printed circuit board 100 is also populated with various components 130, 132, 134, 138, 1000. The components 130, 132, 134, 138, 1000 can be either discrete components, or semiconductor chips which include thousands of transistors. The components 130, 132, 134, 138, 1000 can use any number of technologies to connect to the exterior surface 120 of the printed circuit board 100. For example, pins may be inserted into plated through holes, or pins may be extended through the printed circuit board 100. An alternative technology is surface mount technology, where an electrical component, such as component 1000, mounts to an array of pads on the exterior surface 120 of the printed circuit board 100. For example, component 1000 could be a ball grid array package or device that has an array of balls or bumps that interact or are connected to a corresponding array of pads on the exterior surface 120 of the printed circuit board 100. The electrical device or component 1000 includes a package substrate 600 and a die 1010 (shown in
The printed circuit board 100 can also include traces 110 for making external connections to other electrical or electronic devices. In an embodiment of the invention, the component 1000 is a central processing chip or microprocessor, that can be used as a controller or for any other function. Although the printed circuit board 100 shown is a daughter board, the printed circuit board 100 could also be a motherboard, and the component or electrical device could be the main processing unit for a computer. In some computing environments, multiple main processing units can be used.
As shown in
The unfinished package substrate 200 includes a land pad major surface side 310 (shown in
Now referring to
As shown in
The plating layer 522, in an embodiment includes a layer of nickel and a layer of gold. In order to obtain different layers, the plating package 500 must be placed in different electrolytic solutions to produce layers of different compositions. While in each solution, the source of current 510 is enabled for a selected amount of time to produce a plating layer or a portion of a plating layer 522 of a selected thickness. After the plating layer 522 has been deposited, the plating package 500 is disassembled. The conductive adhesive layer 410 generally is used only one time. Therefore the conductive adhesive layer 410 is discarded.
A first clamp 910 and a second clamp 912 capture the land pad major surface 320 of each of the package substrates 200. Clamp 910 has an opening therein, which allows a portion of the metal plate 810 to extend beyond the clamp so that it can be connected to a source of current 900. The source of current 900 is attached to the metal plate 810. The reusable conductive portion 800 sandwiched between the two package substrates 200, and clamped with clamps 910 and 912, forms an plating package 950. The clamps 910, 912 assure that the land pad major surface 310 and the contacts the land pads 312 are substantially sealed from an electrolytic solution. The electrolytic package 950 can then be placed into an electrolytic solution. While the plating package 950 is placed in the electrolytic solution, the source of current 900 is enabled for a selected amount of time to plate the wire bond pads of the bond fingers 322. In an embodiment of the invention, the wire bond pads of the bond fingers 322 are provided with a plating layer 522. In an embodiment of the invention, the plating layer 522 includes at least a layer of nickel and a layer of gold plating. The gold plating provides for a reliable bond between the wires of a die and the plating layer 522 on the wire bond pad of the bond finger 322. After a plating layer 522 is formed on the wire bond pad of the bond finger 322 or on all the bond fingers of the package substrates 200, 200′, the electrolytic plating package 950 is disassembled. As previously mentioned, the conductive cushion sheet attached to the metal plate 810, as well as the seals 830, 832, are reusable. As a result, another pair of package substrates can be used to sandwich the reusable conductive portion 800 and the electrolytic plating process can be repeated.
In an embodiment of the method 1200, placing a deformable conductor in contact with the second major surface and the second pad of one of the plurality of substrates 1212 includes placing a first side of a deformable conductor in contact with the second major surface and the second pad of the one of the plurality of substrates. In another embodiment, placing a deformable conductor in contact with the second major surface and the second pad of another of the plurality of substrates 1212 includes placing a second side of a deformable conductor in contact with the second major surface and the second pad of the one of the plurality of substrates. The method 1212 also includes substantially sealing the second major surface of the one of the plurality of substrates from the electrolytic solution 1218.
Another embodiment of the method 1200 includes substantially sealing the second major surface of the one of the plurality of substrates from the electrolytic solution, and substantially sealing the second major surface of the one of the plurality of substrates from the electrolytic solution. In an embodiment, the deformable conductor includes a conductive adhesive tape. In another embodiment, the deformable conductor includes a metal plate, a first conductive sheet on a first side of the metal plate, and a second conductive sheet on a second side of the metal plate. The method 1200 also includes applying a current to the deformable conductor 1220.
As shown in
As shown in
The foregoing description of the specific embodiments reveals the general nature of the inventive subject matter sufficiently that others can, by applying current knowledge, readily modify and/or adapt it for various applications without departing from the generic concept, and therefore such adaptations and modifications are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments.
It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Accordingly, the embodiments of the invention are intended to embrace all such alternatives, modifications, equivalents and variations as fall within the spirit and broad scope of the appended claims.
Claims
1. A method for plating a first pad on a first major surface of a substrate, the substrate having a first major surface and a second major surface, the method comprising:
- connecting the first pad on the first major surface to a second pad on a second major surface of the substrate;
- applying a voltage to the second pad; and
- placing the first pad on the first major surface into an electrolytic solution.
2. The method of claim 1 further comprising masking portions of the first major surface to selectively prevent plating on portions of the first major surface.
3. The method of claim 1 wherein connecting the first pad on the first major surface to a second pad on the second major surface includes connecting the first pad and the second pad through a via.
4. The method of claim 1 further comprising sealing the second major surface from the electrolytic solution.
5. The method of claim 4 wherein sealing the second major surface from the electrolytic solution includes placing a conductive adhesive tape over the second major surface.
6. The method of claim 1 wherein applying a voltage to the second pad includes:
- placing an electrical conductor having a deformable portion in contact with the second pad; and
- applying the voltage to the electrical conductor.
7. A method for plating a first pad on a first major surface on each of a plurality of substrates, each substrate having a first major surface and a second major surface, the method comprising:
- connecting the first pad on the first major surface to a second pad on a second major surface of the substrate through a via in the substrate;
- placing a deformable conductor in contact with the second major surface and the second pad of one of the plurality of substrates;
- placing a deformable conductor in contact with the second major surface and the second pad of another of the plurality of substrates; and
- applying a voltage to the deformable conductor.
8. The method of claim 7 further comprising placing the first pad on the first major surface of the one of the plurality of substrates and another of the plurality of substrates into an electrolytic solution.
9. The method of claim 7 wherein placing a deformable conductor in contact with the second major surface and the second pad of one of the plurality of substrates includes placing a first side of a deformable conductor in contact with the second major surface and the second pad of the one of the plurality of substrates
10. The method of claim 9 wherein placing a deformable conductor in contact with the second major surface and the second pad of another of the plurality of substrates includes placing a second side of a deformable conductor in contact with the second major surface and the second pad of the one of the plurality of substrates.
11. The method of claim 8 further comprising substantially sealing the second major surface of the one of the plurality of substrates from the electrolytic solution.
12. The method of claim 8 further comprising:
- substantially sealing the second major surface of the one of the plurality of substrates from the electrolytic solution; and
- substantially sealing the second major surface of another of the plurality of substrates from the electrolytic solution.
13. The method of claim 7 wherein the deformable conductor includes a conductive adhesive tape.
14. The method of claim 7 wherein the deformable conductor includes:
- a metal plate;
- a first conductive sheet on a first side of the metal plate; and
- a second conductive sheet on a second side of the metal plate.
15. The method of claim 7 further comprising clamping the one of the plurality of substrates, the other of the plurality of substrates, and the deformable conductor together.
16. An apparatus comprising:
- a first package substrate, further including: a first major surface having a first pad; a second major surface having a second pad; and an electrical pathway in the first package substrate between the first pad and the second pad; and
- a deformable conductor in electrical communication with the second major surface and the second pad.
17. The apparatus of claim 16 further comprising a second package substrate, further including:
- a third major surface having a third pad;
- a fourth major surface having a fourth pad; and
- an electrical pathway in the second package substrate between the third pad and the fourth pad, wherein the deformable conductor is in electrical communication with the fourth major surface and the fourth pad.
18. The apparatus of claim 17 wherein the deformable conductor is a conductive adhesive tape.
19. The apparatus of claim 17 wherein the deformable conductor comprises:
- a metal plate;
- a first conductive sheet on a first side of the metal plate; and
- a second conductive sheet on a second side of the metal plate.
20. The apparatus of claim 19 further comprising a seal coupled to the metal plate, the seal positioned to substantially seal the second pad and the fourth pad from an environment surrounding the first package substrate and the second package substrate.
21. The apparatus of claim 19 further comprising a source of current communicatively coupled to the metal plate.
22. The apparatus of claim 16 further comprising a source of current communicatively coupled to the deformable conductor.
23. The apparatus of claim 16 further comprising an electrolytic bath in fluid communication with the first package substrate.
24. The apparatus of claim 17 further comprising an electrolytic bath in fluid communication with the first package substrate and the second package substrate.
25. An apparatus comprising:
- a first package substrate further comprising: a first major surface having a first pad; a second major surface having a second pad; and an electrical connection between the first pad and the second pad;
- a second package substrate further comprising: a third major surface having a third pad; a fourth major surface having a fourth pad; and an electrical connection between the third pad and the fourth pad; and
- a deformable conductor sandwiched between the first package substrate and the second package substrate.
26. The apparatus of claim 25 wherein the deformable conductor deforms to make electrical contact with the second pad and the fourth pad.
27. The apparatus of claim 25 wherein the electrical connection between the first pad and the second pad is a via within the first package substrate, and wherein the electrical connection between the third pad and the fourth pad is a via within the second package substrate.
28. The apparatus of claim 25 further comprising a seal separating the second pad and the fourth pad from an environment in contact with the first pad and the third pad.
29. The apparatus of claim 25 further comprising:
- an electrolytic fluid in fluid communication with the first pad and the third pad; and
- a seal preventing fluid communication of the second pad and the fourth pad with the electrolytic fluid.
Type: Application
Filed: Jun 30, 2004
Publication Date: Jan 5, 2006
Inventor: Kumamoto Takashi (Tsukuba)
Application Number: 10/881,016
International Classification: C25D 5/02 (20060101);