Chip on Film Package Reinforcing Sheet for Fine-Pitch Circuit Protection

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Solution Overview

Problem

The increasing demand for high-performance IC packages with finer pitch external contacts makes the fine-pitch circuits in chip on film (COF) packages more vulnerable to breakage, leading to reduced yield rates due to their reduced thickness and mechanical fragility.

Innovation Solution

A chip on film package design that incorporates a reinforcing sheet with flexibility equal to or greater than the base film, disposed on the surface and/or covering the patterned circuit layer, to provide protection and mechanical strength to the fine-pitch circuits, along with an underfill and adhesive layer for enhanced durability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the pitch of external contacts is reduced to increase integration density, then the number of terminals per unit area increases, but the circuit thickness is reduced making the circuit more vulnerable to breakage

Engineering Contradiction:

Improvenumber of external terminals per unit areaVSAvoidmechanical strength of fine-pitch circuit

Core Design Contradiction:

Quantity of substanceVSStrength

Solution Approach 1:

A flexible reinforcing sheet is bonded to the base film to provide mechanical strength to the fine-pitch circuit while maintaining the flexibility required for COF package operation. The reinforcing sheet has flexibility substantially equal to or greater than the base film, preventing circuit breakage during bending or impact.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The base film is combined with a reinforcing sheet to create a composite structure. This composite material provides both the flexibility of the base film and the mechanical strength of the reinforcing sheet, resolving the contradiction between fine pitch requirements and circuit vulnerability.

Inventive Principle:

Principle #40Composite materials

2Manufacturing precision

If the circuit thickness is reduced to achieve finer pitch, then the integration density increases, but the circuit becomes more vulnerable and easier to break

Engineering Contradiction:

Improvecircuit pitch precisionVSAvoidcircuit resistance to breakage

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The flexible reinforcing sheet is bonded to the base film to provide mechanical strength to the fine-pitch circuit while maintaining the flexibility required for COF package operation. The reinforcing sheet has flexibility substantially equal to or greater than the base film, preventing circuit breakage during bending or impact.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The reinforcing sheet is bonded to the base film in advance to provide mechanical strength and prevent circuit breakage before the package undergoes bending or impact during operation or assembly.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Strength

If a rigid reinforcing structure is added to protect the fine-pitch circuit, then the mechanical strength increases, but the flexibility of the package is reduced

Engineering Contradiction:

Improveprotection against circuit fractureVSAvoidflexibility of the package

Core Design Contradiction:

StrengthVSAdaptability or versatility

Solution Approach 1:

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The flexibility parameter of the reinforcing sheet is specifically selected to be substantially equal to or greater than that of the base film, ensuring that the reinforced structure maintains the required flexibility for COF package applications while providing necessary mechanical protection.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11569162B2Chip on film package with reinforcing sheet and manufacturing method of chip on film package with reinforcing sheet

Publication Date: 2023.01.31 NOVATEK MICROELECTRONICS CORP

AI summary

A chip on film package includes a base film, a patterned circuit layer, a chip and a reinforcing sheet. The base film includes a first surface, a second surface opposite to the first surface and a mounting region located on the first surface. The patterned circuit layer is disposed on the first surface. The chip is mounted on the mounting region and electrically connected to the patterned circuit layer. The reinforcing sheet is disposed on the first surface and/or the second surface and exposes the chip, wherein a flexibility of the reinforcing sheet is substantially equal to or greater than a flexibility of the base film.