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Method for embedded plated through-holes in an organic substrate core

IP.com Disclosure Number: IPCOM000007811D
Publication Date: 2002-Apr-24
Document File: 4 page(s) / 105K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for embedded plated through-holes (PTHs) in an organic substrate core. Benefits include improved throughput.

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Method for embedded plated through-holes in an organic substrate core

Disclosed is a method for embedded plated through-holes (PTHs) in an organic substrate core. Benefits include improved throughput.

Background

              The conventional process of drilling and plating contribute to product cost. The epoxy material with the required filler is cured to form the core. Holes are drilled through this core material, followed by electroplating to form the walls of the PTH. The area inside the copper walled holes is filled with an organic material. By some estimates, drilling PTHs in a core contributes about 12% of the substrate cost.

General description

              The disclosed method utilizes a low-cost approach for embedding conductors in an organic core to function as plated through-holes in the substrate. The key element of this process is in the way the plated through-holes are formed in a substrate with an organic core. The conventional drilling, and copper electroplating steps are replaced by punching a copper wire of the required thickness through the core material in the green state, then curing the sheet to form the core. The processes to form the build-up layers remain the same.

Advantages

              The disclosed method provides advantages, including:

§         Reduced cost

§         Simplicity of process

Detailed description

              The disclosed method includes a wire dispenser that embeds the copper wire in green epoxy material that contains the appropriate filler material (see Figure 1a). The dispensing head can be preprogrammed to embed the wires in the required pattern on the epoxy material. Some copper wire is exposed through both surfaces of the core (see Figure 1b) to form PTH lands. The green epoxy is cured (see Figure 1c) to firmly embed the copper wires in the epoxy medium. A mechanical press is used to form lands on either side of the copper wire (see Figure 1d), using the wire that protrudes through the surface.

              Embedding the copper wires on the core prior to epoxy curing reduces buckling because epoxies are extremely compliant in their green state. Critical load for buckling for a 150-micron diameter via is 140N (see Figure 2). As long as the load required to push the wire through the core...