Non Conductive Film with Groove Structure for 3D Chip Stacking

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Solution Overview

Problem

In three-dimensional wafer packaging, the Non Conductive Film (NCF) extrudes outside chips during the Thermal Compression Bond (TCB) process, forming a thick barrier layer that affects the stacking of subsequent chips.

Innovation Solution

A Non Conductive Film composed of a first film layer with a grid-shaped groove structure and a second film layer, where the fluidity of the first film layer is greater than the second film layer, preventing excessive extrusion by providing a supporting effect during chip bonding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a relatively thick NCF barrier layer is formed at the edge of the chip to protect the bump during TCB process, then the protection effect is improved, but the extruded NCF affects the stacking of the next chip

Engineering Contradiction:

Improvebump protectionVSAvoidchip stacking

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The NCF is segmented into two distinct layers: a first film layer with higher fluidity for bump protection and a second film layer with lower fluidity to control extrusion. This segmentation allows each layer to perform its specific function independently, resolving the contradiction between protection and stacking ease.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the NCF are assigned different fluidity properties through the two-layer structure. The first film layer has higher fluidity localized at the bump area for protection, while the second film layer has lower fluidity at the edge regions to prevent excessive extrusion during stacking.

Inventive Principle:

Principle #3Local quality

2Area of stationary object

If the NCF is bonded to the whole wafer for bump protection, then the protection coverage is improved, but the NCF extrudes outside the chips during TCB process

Engineering Contradiction:

Improveprotection coverageVSAvoidNCF extrusion

Core Design Contradiction:

Area of stationary objectVSLoss of substance

Solution Approach 1:

The fluidity parameter of the NCF is changed across different layers. The first film layer maintains higher fluidity to ensure comprehensive bump protection coverage, while the second film layer has reduced fluidity to minimize material extrusion during the TCB process, thus resolving the contradiction between coverage and material loss.

Inventive Principle:

Principle #35Parameter changes

3Strength

If heating and extruding force is applied during TCB process to bond chips, then the bonding strength is improved, but the NCF is extruded outside the chips

Engineering Contradiction:

Improvebonding strengthVSAvoidNCF extrusion

Core Design Contradiction:

StrengthVSLoss of substance

Solution Approach 1:

The NCF is constructed as a composite material system with two film layers having different fluidity characteristics. This composite structure allows the material to exhibit both high bonding strength under compression and controlled extrusion behavior, resolving the contradiction between bonding strength and material loss.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The extrusion force that would normally cause harmful NCF material loss is converted into a beneficial effect by the second film layer's low fluidity, which channels and controls the extrusion. The controlled extrusion actually helps expel air bubbles and ensures complete bonding while minimizing waste.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

Prevents excessive NCF from being extruded outside the chips, ensuring proper stacking and packaging without interfering with subsequent chip layers.

Implementation Method 1

Fluidity of the first film layer is greater than fluidity of the second film layer under a same condition

Methodology Applied

Scientific EffectFluidity difference:

Implementation Method 2

the chips are bonded together through a Thermal Compression Bond (TCB) process

Methodology Applied

Scientific EffectThermal compression:

Data Source

PatentUS20230215832A1Non conductive film, method for forming non conductive film, chip package structure, and method for packaging chip

Publication Date: 2023.07.06 CHANGXIN MEMORY TECH INC

AI summary

A Non Conductive Film (NCF) at least includes a first film layer and a second film layer. A surface of the first film layer is provided with a grid-shaped groove structure, and a depth of each groove of the groove structure is less than a thickness of the first film layer. The second film layer is located in the groove in the surface of the first film layer. The fluidity of the first film layer is greater than the fluidity of the second film layer under the same condition.