Two-step die attach for reduced semiconductor pedestals
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Solution Overview
Problem
Conventional semiconductor packaging technologies face challenges in using reduced area leadframe pedestals due to insufficient adhesion of uncured die attach materials, leading to displacement of laminate components during transportation, which results in scrapped packages and limited feature size in metal layers, affecting device performance.
Innovation Solution
A two-step die attach dispense method using a combination of ultraviolet-curing and thermally-curing die attach materials, where the UV-curing material provides initial mechanical stability and the thermally-curing material ensures robust adhesion, allowing the use of smaller area pedestals while maintaining device functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If pedestal area is reduced to increase metal layer feature size, then laminate component performance is improved, but adhesion stability deteriorates causing component displacement
Solution Approach 1:
The patent divides the die attach material application into two distinct segments: a first die attach material applied to a first portion of the pedestal, and a second die attach material applied to a second portion of the pedestal. This segmentation allows each material to be optimized for its specific function - one for initial adhesion and one for final bonding - thereby resolving the contradiction between using smaller pedestals and maintaining adhesion stability.
Solution Approach 2:
The patent changes the parameters of the die attach materials by using two different materials with different properties rather than a single material. The first material is selected from specific groups (epoxy, polyimide, acrylic) while the second material is selected from different groups (silver epoxy, gold epoxy, palladium epoxy). This parameter change enables the system to achieve both small pedestal area and reliable adhesion through material differentiation.
2Device complexity
If single-step die attach material is used, then process complexity is reduced, but adhesion reliability deteriorates during transportation
Solution Approach 1:
The patent segments the die attach process into two distinct steps with different materials applied to different portions of the pedestal. The first die attach material provides initial adhesion to prevent displacement during transportation, while the second die attach material provides final bonding after curing. This segmentation resolves the contradiction by accepting increased process complexity as the necessary means to achieve reliable adhesion throughout the manufacturing and transportation process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables reliable transportation and secure mounting of laminate components on reduced area pedestals, enhancing device performance by increasing feature size without significant process cycle time increase and minimizing package failures.
Implementation Method 1
A cured first die attach (DA) material may be on an outer edge of the pedestals being an ultraviolet (UV)-curing DA material having a photoinitiator
Implementation Method 2
A cured thermally-curing DA material may be on an area of the pedestals not occupied by the UV-curing DA material
Data Source
AI summary
A packaged semiconductor device includes a leadframe (LF) having a plurality of laminate-supporting pedestals. A cured first die attach (DA) material is on an outer edge of the pedestals being an ultraviolet (UV)-curing DA material having a photoinitiator or a cured B-stage DA material. A cured thermally-curing DA material is on an area of the pedestals not occupied by the UV-curing DA material. A laminate component having bond pads on a top side is mounted top side up on the plurality of pedestals.