CSP Underfill Adhesion Control via Photosensitive Material Removal
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Solution Overview
Problem
In chip size packages (CSPs) of CMOS image sensors, the underfill resin can creep up the side surfaces, causing damage and peeling issues due to the use of elastic bodies, which can break the resin structure and lead to reliability concerns.
Innovation Solution
The CSP is designed with structures that prevent underfill adhesion to the side walls, such as removing photosensitive materials, forming hydrophobic layers, or creating concavities/convexities on the substrate surfaces to inhibit underfill adherence, ensuring the underfill only contacts the bottom surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an elastic body is added to the side surface to adjust stress and prevent chip end damage, then the mounting reliability is improved, but the structure including the resin may break and the elastic body may peel off
Solution Approach 1:
The invention removes the elastic body from the side surface that was causing structural damage and peeling issues. Instead of adding the elastic body to adjust stress, the patent extracts this problematic component entirely and replaces it with a photosensitive material-based solution that achieves stress management without compromising structural integrity.
Solution Approach 2:
The invention changes the material parameter from an elastic body to a photosensitive material that can be selectively removed. This parameter change allows the underfill to be controlled in its adhesion properties - the photosensitive material can be removed by light exposure to create non-adhesive regions, preventing both chip end damage and structural breakdown while maintaining mounting reliability.
2Reliability
If the underfill resin creeps up the side surface of the chip, then the chip end damage is prevented, but the elastic body breaks the resin structure and causes peeling
Solution Approach 1:
The invention introduces a photosensitive material as an intermediary layer between the underfill resin and the chip side surface. This intermediary can be selectively removed by light exposure to create controlled non-adhesive regions, allowing the underfill to creep up for protection without the elastic body's harmful structural interference. The photosensitive material mediates the interaction between underfill and chip, enabling beneficial adhesion while preventing detrimental effects.
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 maintains the mounting reliability of the underfill by preventing it from adhering to the side walls, thus avoiding damage and peeling, and ensuring the underfill's original function is not impaired.
Implementation Method 1
a hydrophobic material is formed on a part or substantially a whole of a side wall of the CSP and thereby the underfill is prevented from adhering to the part or substantially the whole of the side wall of the CSP
Data Source
AI summary
The present disclosure relates to a semiconductor device, an electronic device, and a manufacturing method that can maintain the mounting reliability of an underfill. A chip is formed by a circuit 5 of an imaging element being produced on a Si substrate that is a first substrate and a second substrate being produced on an adhesive formed on the circuit. In this event, a photosensitive material is formed around the chip after the chip is mounted on a mounting substrate by a solder ball or in the state of the chip, then an underfill is formed, and then only the photosensitive 10 material is dissolved. The present disclosure can be applied to, for example, a CMOS solid-state imaging sensor used for an imaging device such as a camera.