Flexible PCB Stiffener Adhesion via Infrared-Reflective Insulator Film

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Solution Overview

Problem

Stiffener detachment during the reflow process is a challenge in stiffener-integrated flexible printed circuit boards, particularly when using black insulator films, due to infrared radiation absorption leading to surface temperature increase and outgassing, which compromises electrical insulation reliability.

Innovation Solution

Incorporating a black coloring agent with a reflective range within the infrared range into the insulator film, along with a binder polymer, to prevent outgassing and enhance electrical insulation reliability, while maintaining adhesiveness between the stiffener and the insulator film.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of information

If a black insulator film is used to conceal the circuit pattern, then the concealment property is improved, but the stiffener detachment during reflow process worsens due to infrared radiation absorption

Engineering Contradiction:

Improveconcealment propertyVSAvoidstiffener adhesion

Core Design Contradiction:

Loss of informationVSReliability

Solution Approach 1:

The patent changes the optical parameters of the insulator film by selecting a black coloring agent with specific infrared reflectivity properties. The key parameter change is the infrared reflectivity (made it large) while maintaining black color for concealment, thus preventing thermal damage during reflow processing

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The insulator film is designed as a composite material containing a binder polymer and a specific black coloring agent. This composite structure combines the mechanical properties of the polymer with the optical properties of the coloring agent that reflects infrared radiation, achieving both concealment and thermal protection

Inventive Principle:

Principle #40Composite materials

2Loss of information

If the insulator film absorbs infrared radiation to provide black color, then the concealment property is improved, but the surface temperature increase and outgassing worsen electrical insulation reliability

Engineering Contradiction:

Improveconcealment propertyVSAvoidelectrical insulation reliability

Core Design Contradiction:

Loss of informationVSReliability

Solution Approach 1:

The patent converts the harmful infrared absorption into a beneficial property by selecting a black coloring agent that reflects infrared radiation. This transforms the potential harm (thermal damage) into a benefit (thermal protection), maintaining concealment while preventing outgassing and insulation failure

Inventive Principle:

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

Solution Approach 2:

The patent changes the thermal-optical parameters of the insulator film by selecting a black coloring agent with high infrared reflectivity. This parameter change prevents excessive temperature rise during reflow, maintaining electrical insulation reliability while preserving the black color for concealment

Inventive Principle:

Principle #35Parameter changes

3Loss of information

If conventional black coloring agents are used in the insulator film, then the concealment property is improved, but the adhesiveness between stiffener and insulator film deteriorates during reflow process

Engineering Contradiction:

Improveconcealment propertyVSAvoidadhesiveness

Core Design Contradiction:

Loss of informationVSStrength

Solution Approach 1:

The patent changes the thermal parameters of the insulator film by selecting a black coloring agent with high infrared reflectivity. This prevents excessive temperature rise that would degrade the adhesive, thereby maintaining adhesiveness during reflow while preserving concealment

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The insulator film is designed as a composite of binder polymer and infrared-reflective black coloring agent. This composite structure provides both concealment and thermal stability, protecting the adhesive bond strength during reflow processing

Inventive Principle:

Principle #40Composite materials

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

The solution effectively prevents stiffener detachment during reflow processes and ensures excellent electrical insulation reliability by reflecting infrared radiation and reducing outgassing, thereby improving the overall performance of stiffener-integrated flexible printed circuit boards.

Implementation Method 1

a black coloring agent having a reflective range within an infrared range

Methodology Applied

Scientific EffectInfrared radiation reflection: Reflection

Implementation Method 2

infrared radiation absorption leading to surface temperature increase

Methodology Applied

Scientific EffectInfrared radiation: Infrared Radiation

Data Source

PatentUS10292262B2Reinforcing-plate-integrated flexible printed circuit board

Publication Date: 2019.05.14 KANEKA CORP

AI summary

The present invention provides a stiffener-integrated flexible printed circuit board that has excellent electrical insulation reliability and that prevents the stiffener from being detached during a reflow process. The stiffener-integrated flexible printed circuit board including: (A) a stiffener, (B) a thermosetting adhesive, (C) an insulator film, and (D) a wiring-pattern-equipped film, (A) the stiffener, (B) the thermosetting adhesive, (C) the insulator film, and (D) the wiring-pattern-equipped film being laminated in this order, (C) the insulator film containing at least (a) a binder polymer and (b) a black coloring agent having a reflective range within the infrared range.