Carrier strip and molded flex circuit ball grid array and method of making

• US 6,124,637 A
• Filed: 09/25/1998
• Issued: 09/26/2000
• Est. Priority Date: 04/24/1996
• Status: Expired due to Term

• Current Assignee: Amkor Technology Singapore Holding Pte., Ltd. (Amkor Technology Incorporated)
• Original Assignee: Amkor Technology Incorporated
• Inventors: Darveaux, Robert F., Freyman, Bruce J.
• Primary Examiner(s): Chaudhuri, Olik
• Assistant Examiner(s): Wille, Douglas A.
• Application Number:
  US09/161,189
• Time in Patent Office: 732 Days
• Field of Search: 257/736, 257/692
• US Class Current: 257/736
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/16237 the bump connector connecting to a bonding area disposed in a recess of the surface of the item
• CPC Class Codes: H01L 2224/32225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/45099 Material
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48227 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2224/854 with a principal constituent of the material being a metal or a metalloid, e.g. boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po), and alloys thereof
• CPC Class Codes: H01L 23/3128 the substrate having spherical bumps for external connection
• CPC Class Codes: H01L 23/49816 Spherical bumps on the substrate for external connection, e.g. ball grid arrays [BGA]
• CPC Class Codes: H01L 23/4985 Flexible insulating substrates H01L23/49572 and H01L23/49855 take precedence
• CPC Class Codes: H01L 24/48 of an individual wire connector
• 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 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• 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 2924/01078 Platinum [Pt]
• CPC Class Codes: H01L 2924/07802 not being an ohmic electrical conductor
• CPC Class Codes: H01L 2924/14 Integrated circuits
• CPC Class Codes: H01L 2924/15311 being a ball array, e.g. BGA
• CPC Class Codes: H01L 2924/181 : Encapsulation
• CPC Class Codes: H01L 2924/207 : Diameter ranges

Abstract

A grid array assembly method and apparatus uses a flex circuitry substrate and includes providing a series of conforming flex circuitry substrates, the flex circuitry substrates include bonding pads and metallization on a first surface and, holes in the substrate which define a contact pad array on the opposite surface. The substrates are tested and acceptable, then mounted on a carrier strip with longitudinally aligned apertures. The carrier strip is typically a metal such as copper. The strip with mounted substrates is then passed to a station where an IC die is mounted on the substrate first surfaces wire bonds are placed from the die to the bonding pads, and the assembly is encapsulated by auto-molding to form a package body. Subsequently, interconnecting bumps are placed on the contact pads and the assembly is removed from the strip.

Claims

1. An article of manufacture comprising an elongated carrier strip including a series of longitudinally spaced apertures and a series of pre-tested and pre-accepted flex circuitry substrates mounted in seriatim over said apertures along the elongated carrier strip, said elongated carrier strip having a greater stiffness than a stiffness of said flex circuitry substrates, each of said flex circuitry substrates having outer peripheral edges in an adhesive connection directly to respective inner peripheral edges of the elongated carrier strip bounding the apertures in said elongated carrier strip, wherein said elongated carrier strip and said flex circuitry substrates remain connected while assembling the flex circuitry substrates into a grid array package and wherein the elongated carrier strip comprises portions surrounding said apertures that remain attached to said flex circuitry substrates and provide stiffness for said flex circuitry substrates when said flex circuitry substrates are removed from said elongated carrier strip to produce resultant grid array packages.

2. The article of claim 1 further including an integrated circuit die attached to each of said flex circuitry substrates, each said die having conductive pads, bond wires extending from said conductive pads to bonding pads on a first surface of a corresponding flex circuitry substrate, and molded encapsulation over said die, around said bond wire and onto a portion of said first surface of said flex circuitry substrate.

3. The article of claim 2 further including an array of contact pads on an opposite second surface of said flex circuitry substrate and conductive vias extending from said contact pads to metallization on said first surface of said flex circuitry substrate.

4. The article of claim 3 wherein a solder ball extends from each of said contact pads.

5. The article of claim 3 wherein the array of contact pads are defined by a series of holes in the flex circuitry substrates that expose metallization on said first surface.

6. The article of claim 3 wherein the elongated carrier strip apertures are large enough such that all of said metallization is contained within an elongated carrier strip aperture.

7. The article of claim 3 wherein said portion of said elongated carrier strip surrounding said apertures extends from the molded encapsulation and remains attached to the flex circuitry substrate such that said elongated carrier strip portion provides a thermally conductive surface area exposed outside of the package.

8. The article of claim 1 wherein the thermal expansion coefficient of a construction material of the flex circuitry substrate is closely matched to the thermal expansion coefficient of a construction material of said elongated carrier strip.

9. The article of claim 1 wherein said flex circuitry substrates are constructed of polyimide plastic.

10. The article of claim 9 in which said polyimide plastic flex circuitry substrates are on a tape having a thickness of 0.025 mm to 1.25 mm.

11. The article of claim 1 wherein said flex circuitry substrates are mounted in the adhesive connection directly to said peripheral edges of the elongated carrier strip around 360°

of each of said spaced apertures.

12. The article of claim 1 wherein said elongated carrier strip is a semi-flexible web having a rigidity to support the series of flex circuitry substrates in an essentially planar assembly.

13. The article of claim 1 wherein said elongated carrier strip is of steel or brass or aluminum.

14. The article of claim 1 wherein the thermal coefficient of expansion of a construction material of the flex circuitry substrate and the construction material of the elongated carrier strip are both in a range of 12 to 18 ppm/°

C.

15. The article of claim 14 in which the flex circuitry substrate is a polyimide substrate and the elongated carrier strip is of a nickel-plated steel, stainless steel, copper or brass construction.

16. The article of claim 1 wherein the thermal coefficient of expansion (TCE) of the flex circuitry substrates have a TCE equal to 20 to 40 ppm/°

C. and the elongated carrier strip is aluminum.

17. The article of claim 3 wherein said elongated carrier strip portion forms a ground plane with said metallization.

18. Package assemblies comprising:

an elongated carrier strip having a plurality of apertures;

flex circuitry substrates adhesively attached to said elongated carrier strip, each of said flex circuitry substrates covering one of said apertures;

bonding pads disposed on said flex circuitry substrates;

an integrated circuit die coupled to each of said flex circuitry substrates, said integrated circuit dies having die conductive pads;

electrical means coupling said die conductive pads to said bonding pads;

encapsulations covering said integrated circuit dies, said die conductive pads and a portion of each of said flex circuitry substrates not covered by said elongated carrier strip; and

interconnection members communicating with said flex circuitry substrates,

wherein said elongated carrier strip comprises removable portions surrounding said apertures, the removable portions remaining attached to said flex circuitry substrates when said flex circuitry substrates are removed from said elongated carrier strip to produce package assemblies.

19. The package assemblies of claim 18 wherein each of said flex circuitry substrates comprise a plurality of contact pads, wherein all of said contact pads for at least one of said flex circuitry substrates are not covered by said elongated carrier strip.

20. The package assemblies of claim 18 wherein each of said flex circuitry substrates comprise a plurality of contact pads, wherein all of said contact pads for at least one of said flex circuitry substrates are covered by said elongated carrier strip.

21. The package assemblies of claim 18 wherein said flex circuitry substrates are defined by a plastic film having a die attach area, a film metallization, and contact pads, wherein said interconnect members communicate with said contact pads.

22. The package assemblies of claim 21 wherein each of said removable portions forms a ground plane with said metallization.

23. The package assemblies of claim 18 additionally comprising a non-conductive adhesive attaching said elongated carrier strip to said flex circuitry substrates.