Glass Substrate Through-Hole Coating for Thermal Stress Mitigation
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Solution Overview
Problem
Existing methods for mitigating stress in through-glass-vias (TGV) substrates due to thermal expansion mismatch between glass and plated metal vias, such as using glass with higher CTE, plugging vias with dielectric material, or conformal plating, result in compromises in product performance or VIA scaling, bump cracking, and electrical limitations.
Innovation Solution
An apparatus and system for coating glass substrates with a plurality of through-holes using liquid coating, which includes a support frame, dispenser head, and coating units like air blowers or suction heads to infiltrate and coat the inner walls of the through-holes with low modulus, elastic materials before metallization, ensuring the coating permeates and does not fill the holes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If glass with higher CTE is used to mitigate thermal expansion mismatch stress, then stress mitigation is improved, but product performance deteriorates due to FLI stress, bump cracking, and loss of coplanarity during assembly
Solution Approach 1:
The patent introduces an intermediary coating layer between the glass substrate and metal via that acts as a stress buffer. This coating has intermediate CTE properties between glass and metal, absorbing thermal expansion mismatch stress without transmitting it to the glass substrate, thereby preventing both stress-related defects and maintaining product reliability
Solution Approach 2:
The patent modifies the CTE parameter of the interface between glass and metal by introducing a coating layer with specific CTE properties. This changes the thermal expansion characteristics of the composite structure, allowing the system to accommodate thermal cycling without generating excessive stress in the glass substrate
2Stress or pressure
If vias are plugged with dielectric material and drilled with laser to mitigate stress, then stress mitigation is improved, but VIA diameter and bump pitch are reduced due to large laser diameter and process tolerance requirements
Solution Approach 1:
The patent applies coating to the via walls before metallization, creating a pre-compression stress state in the via structure. This preliminary action allows the via to accommodate subsequent thermal cycling without requiring oversized dimensions for stress relief, thereby maintaining small VIA diameter and fine bump pitch
3Stress or pressure
If conformal plating followed by backfill with dielectric material is used to mitigate stress, then stress mitigation is improved, but VIA diameter and bump pitch are reduced due to large holes needed for backfilling and maintaining sufficient metal volume
Solution Approach 1:
The patent extracts the dielectric backfill step from the process, using only conformal coating and metallization. This eliminates the need for large via openings required for backfilling, while the coating layer provides stress mitigation through its intermediate CTE properties, thereby maintaining small VIA diameter and fine bump pitch
4Stress or pressure
If existing stress mitigation methods are used, then thermal expansion stress is reduced, but metal volume is limited leading to electrical limitations
Solution Approach 1:
The coating layer serves as an intermediary that enables thinner via walls while maintaining stress mitigation. This allows increased metal fill ratio within the via without compromising structural integrity, thereby increasing total metal volume and improving electrical performance
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
Mitigates thermal expansion mismatch stress by providing a scalable, high-performance dielectric coating that maintains the integrity of the glass substrate, allowing for effective metallization without compromising mechanical or electrical properties.
Implementation Method 1
a coating unit configured to apply a force on the liquid coating so as to urge the liquid coating to permeate the plurality of through-holes in the glass substrate
Implementation Method 2
the coating unit includes an air blower movable relative to the support frame, wherein the air blower is operable to generate an airflow to spread the liquid coating and push the liquid coating into the plurality of through-holes in the glass substrate
Implementation Method 3
the coating unit includes a suction head at an underneath side of the support frame opposite a topside of the support frame that supports the glass substrate, the suction head being movable relative to the support frame and operable to generate suction through the at least one opening in the support frame so as to draw the liquid coating to permeate the plurality of through-holes of the glass substrate
Data Source
AI summary
An apparatus for coating a glass substrate having a plurality of through-holes, the apparatus including a support frame including one or more abutment portions configured to support the glass substrate in a levelled orientation; a dispenser head operable to deposit a liquid coating on the glass substrate; and a coating unit configured to apply a force on the liquid coating so as to urge the liquid coating to permeate the plurality of through-holes in the glass substrate.