Polymer Substrate IC with Through-Vias for Thermal and Adhesion
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Solution Overview
Problem
Conventional BGA packages face reliability issues due to heat-induced warpage from coefficient of thermal expansion differences and high costs associated with solder ball processing and metal filling in polymer substrates.
Innovation Solution
The use of a polymer substrate with bottom metal pads replacing solder balls, eliminating the need for metal filling and solder resist, and allowing the mold compound to adhere directly to the substrate for improved adhesion and reduced costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder balls are used in conventional BGA packages, then electrical connection is achieved, but reliability deteriorates due to heat-induced warpage from coefficient of thermal expansion differences
Solution Approach 1:
The patent removes solder balls from the package structure entirely, replacing them with through-substrate vias that extend through the polymer substrate to provide direct electrical connection. This extraction of the problematic solder ball component eliminates the adhesion interface that causes reliability issues under thermal stress.
Solution Approach 2:
The patent changes the electrical connection method from solder ball adhesion to through-substrate via connection. The vias are filled with conductive material and extend through the substrate to contact pads on the opposite side, fundamentally changing how electrical connection is achieved and eliminating dependence on solder ball integrity.
2Reliability
If metal filling is performed in the neck region of through-holes, then solder ball retention is improved, but manufacturing cost increases
Solution Approach 1:
The patent eliminates the need for metal filling in the neck region by removing solder balls from the design. The through-substrate vias provide direct electrical connection without requiring additional metal reinforcement in the hole neck, thereby eliminating this complex and costly manufacturing step.
Solution Approach 2:
Instead of filling holes with metal and adding solder balls on top, the patent inverts the approach by creating through-substrate vias that extend through the entire substrate thickness and make direct contact with opposite-side pads, eliminating the need for both metal filling and solder balls.
3Productivity
If conventional BGA packaging is used, then IC device assembly is achieved, but production cost increases due to solder ball processing and metal filling
Solution Approach 1:
The patent removes the costly solder ball processing and metal filling operations from the manufacturing process by replacing them with a simpler through-substrate via structure. The vias are formed and filled during substrate fabrication, eliminating subsequent complex assembly steps.
Solution Approach 2:
The through-substrate vias are formed and prepared during the substrate fabrication process itself, before IC device assembly. This preliminary action integrates the electrical connection structure into the substrate manufacturing, eliminating the need for separate solder ball attachment and metal filling operations.
4Ease of manufacture
If solder resist is applied over metal pattern, then solder ball placement is enabled, but adhesion of mold compound deteriorates
Solution Approach 1:
The patent eliminates solder resist from the structure by removing solder balls. The through-substrate vias provide direct electrical connection without requiring solder resist isolation, allowing mold compound to adhere directly to the polymer substrate surface for improved bonding strength.
Solution Approach 2:
The patent creates a homogeneous interface between mold compound and polymer substrate by eliminating the metal pattern and solder resist layers. This direct contact between mold compound and substrate provides uniform adhesion across the entire surface, improving overall bond strength.
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 solution enhances reliability by eliminating solder adhesion problems and reduces production costs by eliminating solder ball processing and metal filling, while improving thermal dissipation with thermally conductive die attach materials.
Implementation Method 1
improving thermal dissipation with thermally conductive die attach materials
Implementation Method 2
a surface of a polymer layer is covered with a film adhesive that is protected by a removable, protective sheet
Implementation Method 3
The solder balls from the BGA package form solder joints following reflow with conductive contacts on the mother board
Implementation Method 4
heat induced warpage resulting from coefficient of thermal expansion (CTE) differences during the reflow process
Data Source
AI summary
An integrated circuit (IC) device includes a polymer substrate having a topside surface and a bottomside surface opposite the topside surface, a plurality of through-holes that extend from the topside surface to the bottomside surface, and a plurality of bottom metal pads on the bottomside surface positioned over the plurality of through-holes. At least one IC die having an active topside including a plurality of bond pads and a second side is affixed to the topside surface. Bonding features are coupled to the plurality of bond pads for coupling respective ones of the plurality of bond pads to the plurality bottom metal pads. The bonding features extend into the through-holes to contact the bottom metal pads.