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Method for quantitative die-attach metrology

IP.com Disclosure Number: IPCOM000017098D
Publication Date: 2003-Jul-22
Document File: 5 page(s) / 682K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosure outlines a method for quantitative die-attach metrology. Benefits include improved reliability.

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Method for quantitative die-attach metrology

Disclosure outlines a method for quantitative die-attach metrology. Benefits include improved reliability.

Background

      Die attach is one of the most difficult steps in chip assembly. Inadequate die attach causes reliability issues.

      Conventionally, die-related parameters are measured using a measuring scope to locate one point, designated as z=0, on the substrate surface. The single point on the substrate surface does not account for the effects of localized substrate tilt due to warpage. A better method of establishing z=0 plane is to measure multiple points on the substrate surface, e.g., four points at the four die corners.                                                                                                                                 

      Epoxy-related parameters are visually measured by an operator using the naked eye or with the aid of an optical microscope:

(1)   The conventional practice assesses epoxy coverage at 25% for every die edge that epoxy bleed-out is observed. For example, if epoxy bleed-out is observed at 3 die edges, then the coverage is 75%.

(2)   The height of epoxy bleed out is described as a percentage of the die height. Even when aided by an optical microscope, estimates by operators are neither accurate nor precise. Consistency between operators cannot be expected.

General description

              The disclosed method measures parameters related to die and epoxy by using quantitative measuring tools and applying a quantitative computation algorithm. The method includes the following measurements:

•             Die height

•             Die tilt

•             Die warpage

•             Bond line thickness (BLT)

•             Fillet height

•             Epoxy coverage

      The disclosed method uses vision-based coordinate measuring machines that are readily available on the assembly production floor.

      The method proposes a minimum set of points to be measured for optimized accuracy and throughput.

Advantages

              The disclosed method provides advantages, including:

•             Improved reliability due to providing quantitative, repeatable, and reproducible results

Detailed description

              The disclosed method provides consistent inspection results, which are quantitative, repeatable, and reproducible. The method suggests measurements of z=0 plane and die related parameters including height, tilt, warpage, and estimated BLT (see Figure 1).

      The disclosed method quantifies fillet height and epoxy coverage by measuring height and extent of...