Through-Glass Via Electrode Surface Texture for Thermal Shock Reliability
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Solution Overview
Problem
Existing multilayer wiring substrates with through glass vias (TGVs) face issues with thermal shock resistance and connectivity between conductive layers, leading to potential cracking and reliability concerns, particularly when using glass substrates thinner than 300 μm.
Innovation Solution
A multilayer wiring substrate with a glass substrate featuring a through electrode having a bottom surface with unevenness of ±0.5 μm to 5 μm in height, where a hydrofluoric acid resistant metal layer and seed layers are formed on the uneven surface, followed by electrolytic plating to enhance connectivity and thermal shock resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a through glass via is formed to a glass substrate, then connectivity between conductive layers is achieved, but the mechanical strength of the glass substrate deteriorates and glass cracking may occur
Solution Approach 1:
A modified part is formed in the glass substrate at the via position before etching the through glass via. This preliminary modification creates a localized region with altered physical properties that prevents crack propagation during subsequent processing and thermal cycling, thereby maintaining mechanical strength while enabling connectivity.
Solution Approach 2:
The modified part acts as a cushioning region that absorbs and distributes stress concentrations around the via hole. By pre-forming this modified zone, the structure is prepared to withstand thermal expansion differences and mechanical stresses that would otherwise cause cracking in thin glass substrates.
2Length of moving object
If the thickness of glass is reduced to 300 μm or less, then the substrate becomes more suitable for certain applications, but glass cracking occurs during conveyance and processing
Solution Approach 1:
The modified part is formed before any subsequent processing steps. This pre-modification creates a stress-distributing zone that compensates for the reduced mechanical strength inherent in thinner glass substrates, preventing cracking during conveyance and processing despite the reduced thickness.
Solution Approach 2:
The modification is applied locally at the via position rather than throughout the entire substrate. This localized modification strengthens the critical region around the via hole without requiring overall thickening of the substrate, thus maintaining the thin profile while improving crack resistance.
3Ease of operation
If laser treatment is performed before forming conductive parts, then handling of substrate is facilitated and conductive parts are protected from processing heat, but additional process steps are required
Solution Approach 1:
The laser treatment that forms the modified part is combined with the via formation process. The same laser system and processing sequence accomplish both the modification for crack prevention and the preparation for via etching, eliminating the need for separate modification and via formation steps.
4Ease of manufacture
If conventional through glass via formation is used, then manufacturing simplicity is maintained, but thermal shock resistance of through electrode is insufficient
Solution Approach 1:
The modified part is formed in advance before via etching and conductive material deposition. This preliminary step creates a stress-absorbing zone that prevents cracking during thermal cycling, improving thermal shock resistance without adding complex equipment or significantly complicating the manufacturing 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
The approach significantly improves the thermal shock resistance and reliability of the through electrode by increasing the contact area and preventing disconnections during thermal cycles, while reducing via filling failures and air bubble issues during plating.
Implementation Method 1
irradiating a glass substrate having a first surface and a second surface with a laser to form a modified part reaching the first surface in the glass substrate and form, on the first surface of the glass substrate, an unevenness
Implementation Method 2
etching the modified part from the second surface of the glass substrate using an etching liquid to form a through glass via
Implementation Method 3
energizing the second seed layer to perform an electrolytic plating treatment
Data Source
AI summary
A multilayer wiring substrate including a glass substrate provided with a through electrode, in which a bottom surface part of the through electrode provided to the glass substrate contains an unevenness in which an absolute value of a height difference from a first surface of the glass substrate is ±0.5 μm or more and 5 μm or less. For manufacturing this, a glass substrate is irradiated with a laser, a modified part reaching a first surface is formed in the glass substrate, and an unevenness is formed on the first surface of the glass substrate. Then, a hydrofluoric acid resistant metal layer and/or a first seed layer on each of which a shape of the unevenness is transferred is formed. Thereafter, a through glass via is formed by hydrofluoric acid, and then a second seed layer on which the uneven shape is transferred is formed in the through glass via.