High density interconnect substrate

• US 5,891,795 A
• Filed: 03/18/1996
• Issued: 04/06/1999
• Est. Priority Date: 03/18/1996
• Status: Expired due to Fees

• Current Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Swirbel, Thomas J., Arledge, John K.
• Primary Examiner(s): Picardat, Kevin M.
• Application Number:
  US08/617,156
• Time in Patent Office: 1,114 Days
• Field of Search: 257/737, 257/738, 257/751, 257/762, 257/766, 257/773, 257/776, 257/780, 257/786, 438/613, 438/6.4, 438/626, 438/648, 438/650, 438/656, 438/685, 438/686
• US Class Current: 438/613
• CPC Class Codes: H01L 21/4846 Leads on or in insulating or insulated substrates, e.g. metallisation H01L21/4821 takes precedence; metallisation of ceramics in general C04B41/51; printed circuits H05K3/00
• CPC Class Codes: H01L 21/4853 Connection or disconnection of other leads to or from a metallisation, e.g. pins, wires, bumps
• 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 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H05K 2201/0347 Overplating, e.g. for reinforcing conductors or bumps; Plating over filled vias
• CPC Class Codes: H05K 2201/10234 Metallic balls
• CPC Class Codes: H05K 3/4046 using auxiliary conductive elements, e.g. metallic spheres, eyelets, pieces of wire
• CPC Class Codes: H05K 3/4644 by building the multilayer layer by layer, i.e. build-up multilayer circuits making via holes in the insulating layers H05K3/0011; special circuit boards as base or core whereon the multilayer is built H05K3/4602

Abstract

A method of creating high density interlayer interconnects on circuit carrying substrates. A circuit pattern (20) is formed on one side of a substrate (10), and gold balls (30) are selectively placed on the circuit pattern using a thermosonic ball bonder. A liquid solution of a polymer is cast directly on the substrate and the etched circuit pattern such that only the upper portion of each gold ball is revealed when the liquid polymer solution is then dried and cured to form a dry film (40). A second layer of metal is then deposited directly on the dry film, such that it is electrically and mechanically connected to the exposed top of the gold balls. A second circuit pattern (50) is then formed in the second layer of metal. The resulting high density interconnect has two circuit layers separated by a dielectric layer. Each circuit layer is connected to the other by the gold balls that serve as conductive vias.

Claims

1. A method of manufacturing a high density interlayer interconnects for circuit carrying substrates, comprising:

providing a substrate having a first circuit pattern on a major surface thereof;

attaching a gold or copper ball on a portion of the first circuit pattern by means of a ball bonder;

forming a polymer dielectric layer directly on the major surface and directly on the circuit pattern such that an upper portion of the ball is revealed;

depositing a second circuit pattern directly on the polymer dielectric layer in a manner sufficient to electrically and mechanically connect the second circuit pattern to the revealed upper portion of the ball.

2. The method as described in claim 1, further comprising a step, after the step of forming polymer dielectric layer, of descumming the polymer dielectric layer.

3. The method as described in claim 1, wherein the step of forming a polymer dielectric layer comprises applying a liquid solution of a polymer, drying the liquid solution to form a polymer film, and curing the polymer film.

4. The method as described in claim 3, wherein the step of forming a polymer dielectric layer comprises depositing the liquid solution by spinning or spraying or roller coating or doctor blade.

5. The method as described in claim 3, wherein the step of attaching by means of a ball bonder comprises an ultrasonic, thermosonic or thermocompression ball bonding technique.

6. A method of manufacturing a high density interlayer interconnects for circuit carrying substrates, comprising:

providing a printed circuit board having an etched circuit pattern on a major surface thereof, the etched circuit pattern comprising copper with nickel and gold plated thereon;

attaching a plurality of gold balls on a portion of the etched circuit pattern by means of a thermosonic ball bonder;

applying a liquid epoxy polymer directly on the major surface and directly on the etched circuit pattern such that only an upper portion of each of the gold balls is revealed;

curing the liquid epoxy polymer to form a dry film;

sputtering a layer of copper directly on the dry film, such that the layer of copper is electrically and mechanically connected to the revealed upper portion of the gold balls; and

defining a second circuit pattern in the sputtered copper layer.

7. A high density interlayer interconnect for a printed circuit board, comprising:

a printed circuit laminate containing a first circuit pattern on a major surface thereof;

a gold or copper ball bonded to a portion of the circuit pattern;

a polymer dielectric layer covering and in intimate contact with the major surface and the circuit pattern and the ball, and the polymer dielectric layer arranged so that only an upper portion of the ball is revealed; and

a second circuit pattern disposed directly on the dielectric layer and the ball, portions of the second circuit pattern electrically and mechanically attached to the revealed upper portion of the ball to provide a high density interconnection between the first and second circuit patterns.

8. The high density interlayer interconnect as described in claim 7, wherein the first circuit pattern comprises copper with nickel and gold plated thereon.

9. The high density interlayer interconnect as described in claim 7, wherein the gold or copper ball is between 0.02 mm and 0.15 mm.

10. The high density interlayer interconnect as described in claim 7, wherein the polymer dielectric layer is selected from the group consisting of polyimide, polybutadiene, polytetrafluoroethylene, liquid crystal polymer, acrylic, epoxy, and benzocyclobutene.

11. The high density interlayer interconnect as described in claim 7, wherein the second circuit pattern is electroless metal or sputtered metal.