Wafer Placement Table Assembly for Uniform Heat Dissipation
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Solution Overview
Problem
Existing wafer placement tables face issues with thermal uniformity due to the displacement of thermally conductive sheets and variations in screw tightening, leading to inconsistent heat dissipation.
Innovation Solution
A wafer placement table design featuring a ceramic substrate with a support substrate and a heat dissipation sheet that includes projection insertion holes and thermally conductive paste, ensuring the sheet is compressed uniformly and maintaining close contact between substrates for consistent thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the thermally conductive sheet is positioned without a positioning device, then the manufacturing process is simple, but the sheet may be displaced from its original position
Solution Approach 1:
The thermally conductive sheet itself serves as the positioning device through its protruding holes that align with projections on the substrate. The sheet's own structure (the holes) provides the positioning function, eliminating the need for separate positioning devices while maintaining manufacturing simplicity
Solution Approach 2:
The positioning function is localized to specific points where protruding holes are formed in the thermally conductive sheet. These localized features (holes at specific positions) provide precise positioning without requiring the entire sheet to have complex positioning structures
2Ease of operation
If the screw members are tightened with varying degrees, then the assembly process is flexible, but the thermal uniformity of the wafer deteriorates
Solution Approach 1:
Projections are pre-formed on the substrate surface before assembly. These projections serve as stoppers that limit the tightening depth of screw members, ensuring uniform compression of the thermally conductive sheet regardless of variations in tightening force. The preliminary structure (projections) prevents the worsening of thermal uniformity
Solution Approach 2:
The physical state of the thermally conductive sheet is changed from uncompressed to uniformly compressed state. The projections control the compression parameter (thickness reduction) to be uniform across all locations, transforming the sheet into a state that ensures consistent thermal conductivity throughout the assembly
3Ease of manufacture
If gaps exist between the substrates and heat dissipation sheet, then the assembly is easier to manufacture, but thermal resistance increases
Solution Approach 1:
Thermally conductive paste is introduced as an intermediary substance between the substrates and the heat dissipation sheet. This paste fills any gaps or voids that may exist, ensuring continuous thermal contact paths. The intermediary material maintains reliable thermal conductivity while allowing for easier manufacturing with natural tolerances
Solution Approach 2:
The thermally conductive paste is applied in a manner that allows it to flow into and fill porous spaces or gaps between mating surfaces. The paste's fluid state before curing allows it to penetrate and eliminate voids, creating intimate thermal contact without requiring precision manufacturing
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 design enhances thermal uniformity by maintaining consistent heat dissipation across the wafer placement table, reducing thermal resistance, and ensuring efficient heat transfer between substrates.
Implementation Method 1
a thermally conductive paste interposed at least one of between side surfaces of the projections and an inner peripheral surface of the projection insertion hole of the heat dissipation sheet or between top surfaces of the projections and the lower surface of the upper substrate
Implementation Method 2
The heat dissipation sheet is thus easily positioned. The screw member is screwed until an interval between the upper substrate and the lower substrate coincides with the height of each projection. Consequently, the heat dissipation sheet disposed between the upper substrate and the lower substrate is compressed until the thickness of the entirety of the heat dissipation sheet becomes identical or substantially identical to the height of each projection. Therefore, the thermal conductivity of the heat dissipation sheet does not vary greatly depending on locations.
Data Source
AI summary
A wafer placement table includes an upper substrate; a lower substrate; a through hole extending through the lower substrate in an up-down direction; a plurality of projections provided in a dot pattern, for example, at an entirety of an upper surface of the lower substrate and being in contact with the lower surface of the upper substrate; a heat dissipation sheet having a projection insertion hole and being disposed between the upper substrate and the lower substrate; a screw hole provided, in the lower surface of the upper substrate, at a position facing the through hole; a screw member inserted from a lower surface of the lower substrate into the through hole and screwed into the screw hole; and a thermally conductive paste interposed, for example, between side surfaces of the projections and an inner peripheral surface of the projection insertion hole of the heat dissipation sheet.