MEMS Printhead Backside Contacts via Through-Silicon Connectors

Solution Overview

Problem

Existing inkjet printheads face challenges with wirebond connections that protrude from the ink ejection face, affecting print maintenance and quality by preventing a fully planar surface and hindering hydrophobic coatings.

Innovation Solution

The implementation of a printhead assembly with backside electrical connections using a connector film sandwiched between the ink supply manifold and printhead integrated circuits, eliminating the need for wirebonding and ensuring a fully planar ink ejection face by utilizing through-silicon connectors and a tape-automated bonding (TAB) film for power supply.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If wirebond connections are used to supply power to printhead integrated circuits, then electrical connections are established, but the ink ejection face becomes non-planar and print maintenance is hindered

Engineering Contradiction:

Improveelectrical connection reliabilityVSAvoidprint maintenance accessibility

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent inverts the conventional wirebonding approach by moving electrical connections from the frontside (ink ejection face) to the backside of the printhead integrated circuit. Through-silicon connectors are formed extending from the frontside contact pads through the substrate to contact pads on the backside, allowing connector films to make electrical connections without protruding from the ink ejection face, thus maintaining planarity and enabling proper print maintenance

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent transitions electrical connections from a two-dimensional surface arrangement (wirebonds on the frontside) to a three-dimensional through-substrate arrangement. Through-silicon connectors extend vertically through the printhead substrate, moving connection points from the frontside plane to the backside plane, eliminating interference with the ink ejection face while maintaining electrical connectivity

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Reliability

If wirebond connections are used to supply power to printhead integrated circuits, then electrical connections are established, but a fully planar ink ejection face cannot be achieved

Engineering Contradiction:

Improveelectrical connection reliabilityVSAvoidink ejection face planarity

Core Design Contradiction:

ReliabilityVSShape

Solution Approach 1:

The patent inverts the conventional wirebonding approach by moving electrical connections from the frontside (ink ejection face) to the backside of the printhead integrated circuit. Through-silicon connectors are formed extending from the frontside contact pads through the substrate to contact pads on the backside, allowing connector films to make electrical connections without protruding from the ink ejection face, thus maintaining planarity and enabling proper print maintenance

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent extracts the electrical connection function from the frontside ink ejection face and relocates it to the backside of the printhead substrate. By removing wirebonds and their associated support structures from the frontside, the ink ejection face achieves a fully planar surface without protruding elements, while electrical connectivity is maintained through the substrate via through-silicon connectors

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If wirebond connections are used, then power supply is established, but hydrophobic coatings cannot be effectively applied

Engineering Contradiction:

Improvepower supply reliabilityVSAvoidhydrophobic coating uniformity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent extracts the electrical connection function from the frontside ink ejection face and relocates it to the backside of the printhead substrate. By removing wirebonds and their associated support structures from the frontside, the ink ejection face achieves a fully planar surface without protruding elements, while electrical connectivity is maintained through the substrate via through-silicon connectors

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent inverts the conventional wirebonding approach by moving electrical connections from the frontside (ink ejection face) to the backside of the printhead integrated circuit. Through-silicon connectors are formed extending from the frontside contact pads through the substrate to contact pads on the backside, allowing connector films to make electrical connections without protruding from the ink ejection face, thus maintaining planarity and enabling proper print maintenance

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS8506055B2MEMS integrated circuit having backside integrated circuit contacts

Publication Date: 2013.08.13 MEMJET TECH LTD

AI summary

A MEMS integrated circuit includes a silicon substrate having a frontside with a drive circuitry layer and a backside. A MEMS layer is disposed on the drive circuitry layer. The MEMS layer includes a plurality of MEMS devices electrically connected to the drive circuitry layer. Integrated circuit contacts are positioned at a backside of the substrate. The integrated circuit contacts are electrically connected to the drive circuitry layer via respective connector rods extending through the substrate.