Infused Adhesive Segmentation for Optical Sensor Sealing

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Solution Overview

Problem

In electronic devices with stacked configurations, including integrated-circuit chips and protective wafers, achieving a free and leak-tight space between the chip and the protective wafer, especially when the sensor is an optical sensor, is challenging due to the use of transparent protective wafers.

Innovation Solution

A method involving an infused adhesive with curable adhesive and solid spacer elements is used to create a free space between the chip and the protective wafer, with an obstruction barrier formed by the adhesive or an intermediate peripheral ring, allowing for the production of an encapsulation ring that surrounds the chip and protective wafer, ensuring protection from moisture and solid particles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a transparent protective wafer is used for optical sensors, then light transmission is improved, but obtaining a free and leak-tight space between the chip and protective wafer becomes difficult

Engineering Contradiction:

Improvelight transmissionVSAvoidleak-tight space

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The adhesive application is segmented into multiple discrete zones (first adhesive zone, second adhesive zone, third adhesive zone) rather than continuous application. This segmentation allows the adhesive to form discrete barriers that define the free space while maintaining optical transparency where needed.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the protective wafer receive different treatments: the first region has no adhesive applied (maintaining optical path), while the second and third regions have adhesive applied to create the free space boundary and seal. This local differentiation resolves the contradiction between transparency and sealing.

Inventive Principle:

Principle #3Local quality

2Length of stationary object

If adhesive is applied to create a free space between chip and protective wafer, then spacing is achieved, but moisture and particle ingress may occur without proper sealing

Engineering Contradiction:

Improvefree space thicknessVSAvoidmoisture and particle ingress

Core Design Contradiction:

Length of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The adhesive structure is divided into functional segments: spacing zones (second adhesive zone with spacer elements) and sealing zones (first and third adhesive zones forming the obstruction barrier). This segmentation simultaneously achieves free space creation and moisture/particle prevention.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The infused adhesive acts as an intermediary substance that performs multiple functions: it provides mechanical spacing through solid spacer elements, creates hermetic sealing through the obstruction barrier, and allows optical transmission in regions where no adhesive is present.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If an obstruction barrier is formed to prevent moisture ingress, then sealing is improved, but gas escape during curing may be blocked

Engineering Contradiction:

Improvesealing effectivenessVSAvoidcuring process

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The adhesive application is segmented in time and space: adhesive zones are applied first to create the barrier structure, then the protective wafer is positioned to trap air, and finally curing occurs with air escape paths maintained through the segmented adhesive structure rather than a continuous seal.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The adhesive is applied in a preliminary state before final sealing is required. The segmented application pattern is established beforehand to ensure that when the protective wafer is attached and curing occurs, air escape paths are already defined by the adhesive geometry, preventing curing defects.

Inventive Principle:

Principle #10Preliminary action

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 method effectively creates a protected free space between the chip and the protective wafer, preventing moisture and particle ingress while allowing gases to escape during curing, thus safeguarding the sensor and maintaining the integrity of the electronic device.

Implementation Method 1

The curable adhesive of the infused adhesive may be a material capable of curing under the effect of heat.

Methodology Applied

Scientific EffectHeat curing: Heating

Implementation Method 2

The intermediate peripheral ring may be made of a material capable of curing under the effect of ultraviolet radiation.

Methodology Applied

Scientific EffectUltraviolet curing: Photopolymerisation

Data Source

PatentUS11244910B2Method for fabricating an electronic device comprising forming an infused adhesive and a periperal ring

Publication Date: 2022.02.08 STMICROELECTRONICS INT NV

AI summary

A method for fabricating an electronic device includes fixing a rear face of an integrated-circuit chip to a front face of a support wafer. An infused adhesive is applied in the form of drops or segments that are separated from each other. A protective wafer is applied to the infused adhesive, and the infused adhesive is cured. The infused adhesive includes a curable adhesive and solid spacer elements infused in the curable adhesive. A closed intermediate peripheral ring is deposited on the integrated-circuit chip outside the cured infused adhesive, and an encapsulation block is formed such that it surrounds the chip, the protective wafer and the closed intermediate peripheral ring.