Browse Prior Art Database

Method for a LIM electronics package

IP.com Disclosure Number: IPCOM000011513D
Publication Date: 2003-Feb-26
Document File: 8 page(s) / 141K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a liquid injection molded (LIM) electronics package. Benefits include improved reliability, improved functionality, improved throughput, and improved ease of manufacturing.

This text was extracted from a Microsoft Word document.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 36% of the total text.

Method for a LIM electronics package

Disclosed is a method for a liquid injection molded (LIM) electronics package. Benefits include improved reliability, improved functionality, improved throughput, and improved ease of manufacturing.

Background

              Requirements exist for the following:

•             Void-free underfilling of large die flip packages that have small bump pitch and gap height (such as 400 mm2 area with full array 120-µm pitch x 45-µm high bumps) with filled systems (such as >70 wt%)

•             Void-free underfilling and/or overmolding of MMAP substrates that have large area molding arrays with high die density (such as 58 x 58-mm arrays with >25 die per array)

              Conventional solutions include (see Figure 1):

•             Conservative and commercially unacceptable design rules (such as limiting die size, molded matrix array package (MMAP) molding array density and minimum die gap and bump pitch). This solution is unacceptable because ancillary packaging concerns (such as underfilling) do not support market trends toward smaller and thinner packages.

•             Vent holes under the die. This solution uses valuable silicon surface space and diminishes product performance.

•             Vacuum-assisted underfilling/molding. This solution is very expensive and has high processing/maintenance issues.

              LIM is extensively used in the biomedical industry. An existing infrastructure of molding materials, equipment, and tooling can be readily applied to semiconductor packaging.

              Liquid injection molding underfill (LIMUF) systems are comprised of two components that are unreacted until injected into the mold cavity. As a result, they maintain the lower viscosity of their constituent parts.

              MMAP packaging technology includes partially cured (B-staged) resins that are transfer molded into various packaging configurations. Although this technology has found wide usage, it has several limitations related to the melt rheology of the material. The effectiveness of the process is adversely affected when used for underfilling low-K interlayer dielectric (ILD) die. They are prone to cracking when subjected to mechanical loading during assembly operations. MMAP molding compounds have melt viscosities of 10 to 35 Pa-s and require a substantial force to cause the material to flow into small gap areas, such as in underfilling. Typically, these materials require transfer pressures in the range of 6 to 14 MPa to achieve effective transfer and void-free gap filling.

              Conventional molded underfilling (MUF) on low-K ILD die flip-chip assemblies can lead to significant ILD cracking due to large hydrodynamic loads on the die undersurface during gap-filling and packing (see Figure 2).

              Molding can lead to substantial die-lift and significant increases in ILD cracking frequency (see Figure 3). Experiments analyzing molding-induced ILD cracking were performed using molding compounds with a melt viscosit...