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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) / 481K

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...