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eWLB PoP With Cu Leadframe Interposer

IP.com Disclosure Number: IPCOM000248054D
Publication Date: 2016-Oct-21
Document File: 7 page(s) / 512K

Publishing Venue

The IP.com Prior Art Database

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Page 01 of 7

eWLB PoP with Cu Leadframe Interposer

Background

The conventional laminate interposer is essential in the eWLB PoP structure for package integration. However, it is susceptible to warpage concern due to its laminate structure properties mismatch when subjected to thermal and mechanical stresses throughout the entire process. It is rather costly in its fabrication that involved tedious and complicated processes for double sided RDL and TMV (through mold via), as observed using in 2-sided eWLB PoP corresponded to Figure 1A. In another instance for eWLB PoP with PCB bar, the use of PCB bar and separate laminate interposer method as shown in Figure 1B could have plaque with quality issues such as non-wetting and solder bridging during interposer attach process.

Figure 1A: 2-sided eWLB PoP (Prior art)

Figure 1B: eWLB PoP with PCB bar (Prior art)

This invention discloses the use of a bare Cu frame interposer, which features a homogenous and monolithic Cu pillar structure. It has eliminated the need for dielectric in laminate interposer associated with warpage problems, thus renders cost saving through the material and process complexity reductions.

Formation of Cu pillar in bare Cu interposer does not rely on cumbersome processes of TMV (through mold via) and Cu filling since this is achievable simply through half-etching. By resort to the trace tenting pattern artwork for interposer trace layer, it provides design flexibility to allow improvement on the package functional capability as a whole.

There are few concepts of Cu frame interposers corresponding to the diversity of approaches illustrated through the process flows for eWLB PoP in the next section.


Page 02 of 7

eWLB PoP with Cu Leadframe Interposer

Description

The bare Cu frame consists of Cu pillars shown in Figure 2A represented a half-etched Cu leadframe interposer for eWLB PoP. It is constituted with the package by means of compression mold or dielectric film lamination process.

Figure 2A: Half-etched Cu leadframe interposer

To begin with the wafer reconstitution presented in Figure 2B, a mass of eWLB IC chips are inversely placed in well distributed manner on the metal base or carrier laminated with thermal tape, before proceed to compression mold or film lamination process.

Figure 2B: Wafer reconstitution by die attach

By resort to the compression mold method as shown in Figure 2C, the Cu interposer is facing downwards, and positioned with respect to the IC chip on the metal carrier. It is pressed to submerge the Cu pillars into the granular mold compound, while the half-etched recess is filled. The parallelism in mold system enable the Cu interposer attach and molding processes to be completed simultaneously. The mold compound is cured during the in-process stage. Further curing is proceeded by post mold cure (PMC).

Figure 2C: Compression mold and Cu interposer attach parallellism

The metal debond process can then be carried out to remove the metal carrier and thermal ta...