Browse Prior Art Database

Method for the use of BCB-based materials as capillary underfill and associated processing

IP.com Disclosure Number: IPCOM000009291D
Publication Date: 2002-Aug-14
Document File: 7 page(s) / 280K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for the use of benzocyclobutene-based (BCB) materials as capillary underfill and associated processing. Benefits include improved reliability, improved process, and improved throughput.

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 32% of the total text.

Method for the use of BCB-based materials as capillary underfill and associated processing

Disclosed is a method for the use of benzocyclobutene-based (BCB) materials as capillary underfill and associated processing. Benefits include improved reliability, improved process, and improved throughput.

Background

        � � � � � The disclosed method addresses the problem of:

·        Capillary underfill flow problem due to an increased filler-loading requirement for reliability

·        Inter-layer dielectric (ILD) delamination/cracking due to the stress resulted from underfill curing shrinkage and coefficient of thermal expansion (CTE) mismatch during cooling

·        Fillet cracking and delamination of epoxy-based capillary underfill materials due to poor toughness and high moisture absorption, especially for ball-grid array (BGA) packages that require 260°C preconditioning

·        Low manufacturing throughput because epoxy capillary underfill material cannot enable high-temperature snap curing due to voiding

·        Low-temperature shipping and storage. Epoxy-based underfills react and cure slowly at room temperature. Therefore, they must be shipped and stored at –40°C to prevent the curing.

        � � � � � The problems described above are conventionally solved by:

·        Underfill flow problem is mainly solved by improving the wetting property of the formulation, reducing the base resin viscosity and keeping large gap height and bump pitch.

·        ILD delamination/cracking is mainly solved by changing bump metallurgy and ILD material, but these changes normally have major impact on whole package architecture, requiring wide range reassessment.

·        Fillet cracking and underfill delaminating is mainly solved by optimizing underfill material and control of fillet height. However, there is no solution for large-die BGA packages so far.

·        No solution exists to achieve high temperature snap cure for epoxy based capillary underfill material because all epoxy-based underfill materials generate significant amounts of voids when snap cured at a high temperature.

·        No solution exists for the low-temperature shipping and storage.

·        The flexibility to further optimize the epoxy based capillary underfill material is already very low.

        � � � � � Compared to conventional epoxy-based capillary underfill material, BCB-based capillary underfill material has outstanding advantages

. The BCB-based capillary underfill material has much better properties than epoxy-based underfill materials,

including (see Figure 1):

·        Extremely low moisture absorption to eliminate moisture-driven delamination

·        Extremely low shrinkage (0%) during curing to minimize low-K ILD delamination

·        Higher Tg for better reliability with 260°C precondition

·        Low CTE for less silica filler loading to facilitate underfill flow for large die (very possibly a low-cost alternative technology to vacuum assisted technology for large die applications)

·        Low dielectric constant and dissipation factor for better electrical performance

· ...