Fluid Ejection Head Pedestal Void Space Isolates Semiconductor Chip
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Solution Overview
Problem
Fluid ejection heads face challenges due to thermal stress and deformation caused by mismatched coefficients of thermal expansion between silicon chips and thermoplastic bodies, leading to chip distortion and cracking during the manufacturing process and usage.
Innovation Solution
A fluid ejection head design featuring a pedestal with a flexible circuit bonding surface comprising a plurality of ribs and a damage reducing structure, such as a void space or compressible silicone rubber, to isolate the pedestal from the surrounding flexible circuit bonding surface, reducing shock and thermal stress transmission to the chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a thermoplastic body with high CTE is used to attach the silicon chip, then the bonding strength and ease of manufacture are improved, but thermal stress and chip distortion increase due to CTE mismatch
Solution Approach 1:
The patent segments the bonding interface by introducing a pedestal structure with a bonding surface that separates the chip from the main thermoplastic body. This segmentation allows the chip to be bonded to a localized area with controlled thermal properties, reducing the overall thermal stress while maintaining bonding strength.
Solution Approach 2:
The pedestal acts as an intermediary structure between the silicon chip and the thermoplastic body. It provides a bonding surface that mediates the thermal expansion mismatch, allowing the chip to be securely attached while reducing the transmission of thermal stress from the high-CTE thermoplastic material.
2Productivity
If the ejection head size and number of ejection actuators are increased to improve output, then productivity is improved, but manufacturing precision requirements increase and tolerance control becomes more difficult
Solution Approach 1:
The ejection head is segmented into modular components including the pedestal, nozzle plate, and chip assembly. This segmentation allows each component to be manufactured and tested independently, making it easier to control tolerances and maintain precision even as the overall system size and complexity increase.
3Stability of the object's composition
If ceramic substrates are attached to the chip to address thermal compression, then chip stability is improved, but device cost increases substantially
Solution Approach 1:
Instead of using expensive ceramic substrates, the patent employs a cost-effective thermoplastic pedestal structure that provides sufficient thermal stress management. This approach prioritizes adequate performance over maximum durability, using a less expensive material that achieves the necessary chip stability without the high cost of ceramics.
4Stability of the object's composition
If silicon bridges are used in the via area to address thermal stress, then chip stability is improved, but fluid flow problems occur in the chip via area
Solution Approach 1:
The patent segments the structural support function from the fluid flow path by using a pedestal structure located at the periphery of the chip. This separation ensures that stress-management structures do not interfere with the fluid channels, maintaining unobstructed fluid flow while providing necessary chip stability.
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 design effectively reduces chip damage by minimizing stress and deformation, enhancing the reliability and durability of the fluid ejection head components during manufacturing and usage.
Implementation Method 1
Heating the components causes each one to expand according to their respective CTEs. As the parts cool and shrink, the higher CTE plastic body shrinks more than the lower CTE silicon heater chip resulting in thermal stresses on the chip.
Implementation Method 2
A fluid ejection head design featuring a pedestal with a flexible circuit bonding surface comprising a plurality of ribs and a damage reducing structure, such as a void space or compressible silicone rubber, to isolate the pedestal from the surrounding flexible circuit bonding surface, reducing shock and thermal stress transmission to the chip.
Data Source
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AI summary
A fluid ejection head (100) has a fluid supply body (102) having a nosepiece (104) with at least one fluid supply port. A pedestal (108) extends outwards from the exterior surface of the nosepiece (104) near the fluid supply port. A semiconductor chip mounting surface (110) is formed on the pedestal (108). A flexible circuit bonding surface (112), formed by a plurality of ribs (114), also extends outwards from the exterior surface of the nosepiece (104) adjacent the perimeter of the pedestal (108). A damage reducing structure (115) for reducing damage to a semiconductor chip mounted on the pedestal (108) is located between the pedestal (108) and the flexible circuit bonding surface (112). Similarly, a damage reducing structure (115) is located between each adjacent pair of the plurality of ribs (114). In each case, the damage reducing structure (115) may be void space that isolates and reduces damage caused by shock waves traveling through the fluid supply body (102) to the chip mounting surface and the chip mounted thereon.