MEMS Chip Assembly Trenches to Stop Encapsulant Encroachment
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Solution Overview
Problem
The migration of liquid encapsulant onto the surface of MEMS chips, particularly towards MEMS devices, poses a challenge in manufacturing yields as it can irreparably damage the chips, and existing solutions often rely on physical barriers that are undesirable or ineffective.
Innovation Solution
The implementation of shallow encapsulant-retaining trenches on the chip surface between bond pads and MEMS devices, which pin the advancing encapsulant front, preventing its encroachment onto sensitive areas, and the use of grouting trenches between butting printhead chips to minimize grout material encroachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If encapsulant material is applied to cover bond pads and electrical connectors, then electrical connections are protected, but encapsulant migrates onto MEMS device surfaces causing damage
Solution Approach 1:
The chip surface is segmented into distinct regions by etching trenches that separate the bond pad area from the MEMS device area. This physical segmentation creates containment zones that prevent encapsulant material from migrating from the electrical connection region to the MEMS device region, thereby protecting MEMS devices while maintaining encapsulant coverage over bond pads.
Solution Approach 2:
The trench structure acts as an intermediary barrier between the encapsulant material and the MEMS devices. By introducing this intermediate physical feature, the patent prevents direct contact between the harmful encapsulant and the sensitive MEMS devices, while still allowing the encapsulant to fulfill its protective function over the electrical connections.
2Reliability
If dam wall structures are created to block encapsulant migration, then MEMS devices are protected from encapsulant encroachment, but surface projections damage wiper elements during periodic cleaning
Solution Approach 1:
Instead of creating protruding dam walls that extend upward from the surface, the patent inverts the approach by etching trenches that form barriers below or at the surface level. This inverted structure provides the same encapsulant blocking function without creating surface projections that would interfere with wiper elements during cleaning operations.
Solution Approach 2:
The solution moves the barrier function from the vertical dimension (protruding walls) to the horizontal/depth dimension (etched trenches). By creating barriers in the depth dimension through etching rather than adding height through deposition, the patent maintains encapsulant containment while eliminating surface projections that damage wipers.
3Productivity
If multiple trenches are etched into the chip surface to control encapsulant spread, then manufacturing yields increase by preventing MEMS device damage, but chip fabrication complexity increases
Solution Approach 1:
The patent optimizes trench parameters such as depth, width, and spacing to achieve effective encapsulant containment while minimizing fabrication complexity. By carefully selecting these parameters, the trenches provide sufficient barrier function without requiring excessive etching depth or creating overly complex patterns, thus balancing yield improvement with manufacturing simplicity.
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 approach effectively controls the spread of encapsulant and grout materials, reducing damage to MEMS devices and enhancing manufacturing yields by using shallow trenches that maintain structural integrity and prevent encroachment without relying on physical barriers.
Implementation Method 1
each encapsulant-retaining trench being disposed between the bond pads and the MEMS devices, wherein a leading edge of each encapsulant-retaining trench pins an advancing liquid front of the encapsulant material
Data Source
AI summary
A MEMS chip assembly includes: a support structure having a chip mounting surface; a MEMS chip mounted on the chip mounting surface, the MEMS chip having an active surface including one or more rows of MEMS devices and a row of bond pads disposed alongside a connection edge of the MEMS chip and parallel with the rows of MEMS devices; electrical connectors connected to the bond pads; and an encapsulant material covering the electrical connectors. The MEMS chip has a plurality of trenches defined in the active surface, the trenches extending parallel with the rows of MEMS devices and disposed between the bond pads and the MEMS devices. The encapsulant material does not encroach past the trenches towards the MEMS devices.