Liquid Ejection Head Silicon Substrate Through-Hole Cracking Prevention
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Solution Overview
Problem
The existing liquid ejection heads face issues with cracking of the silicon substrate due to the formation of through-holes on the back side, which can lead to damage when external forces are applied, especially since the silicon substrate is prone to cracking in the direction [110].
Innovation Solution
The liquid ejection head design includes through-holes on the back side of the silicon substrate with an outer shape that has no sides parallel to direction [110] or has sides parallel to [110] with a length equal to or less than half the entire length, thereby suppressing cracking by eliminating crack starting points and preventing the advancement of cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If through-holes are bored from the back of the silicon substrate to provide electrically connecting parts, then the electrically connecting parts can be disposed away from the ejection port side, but the silicon substrate is prone to crack in direction [110] when through-holes are arrayed in that direction
Solution Approach 1:
The through-holes are arranged in a direction other than the crystal direction <110> of the silicon substrate, creating an asymmetric arrangement that avoids the high-stress crack propagation path. This asymmetric positioning of through-holes prevents the formation of continuous crack paths along the vulnerable <110> direction while still providing effective electrical connection.
2Ease of manufacture
If through-holes are formed on the back side of the silicon substrate, then electric connection is achieved, but external force can cause cracking of the substrate
Solution Approach 1:
The silicon substrate exhibits different mechanical properties in different crystal directions, with direction <110> being more prone to cracking. By locating through-holes in positions and orientations that avoid this vulnerable direction, the local quality of the substrate is optimized to resist cracking while maintaining electrical connectivity.
Data Source
AI summary
A liquid ejection head includes a recording element substrate including an ejection port member including a liquid ejection port, an electrical wiring layer including a pressure generating element that pressurizes the liquid to eject the liquid and an electrically connecting part connected to the pressure generating element to supply power for driving the pressure generating element to the pressure generating element, and a silicon substrate having the ejection port member and the electrical wiring layer. The silicon substrate includes a through-hole passing through the silicon substrate to expose the electrically connecting part. An outer shape of an opening of the through-hole on the back side of the silicon substrate has no side parallel to direction [110] of the silicon substrate or has a side parallel to the direction [110]. The side has a length equal to or less than half an entire length of the through-hole in the direction [110].