Insulating Layer Gradient for PCB Adhesion
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Solution Overview
Problem
The challenge lies in developing printed circuit boards with thinner, more integrated, and finer circuits that have a coefficient of thermal expansion similar to that of the metal layer, while maintaining adequate insulation and adhesion without the need for additional primer layers, as existing methods struggle with the increased inorganic filler content affecting adhesive strength.
Innovation Solution
A method involving the formation of an insulating layer with a concentration gradient of inorganic filler, achieved by coating a resin composite with a viscosity of 100 Pa·s or less on protective films, drying to precipitate the filler, and laminating protective films without a primer, allowing for improved adhesion and preventing a drop in peel strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If inorganic filler content is increased to match thermal expansion coefficients, then thermal expansion compatibility is improved, but adhesive strength deteriorates
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of inorganic filler within the insulating layer. The filler concentration varies from the first surface to the second surface, with higher concentration at one surface and lower at the other. This localized variation allows the insulating layer to maintain adequate adhesive strength at the metal layer interface while still achieving thermal expansion compatibility through the overall high filler content.
Solution Approach 2:
The patent changes the parameter of filler concentration distribution from uniform to gradient-based. By controlling the concentration gradient of inorganic filler throughout the insulating layer thickness, the patent achieves both thermal expansion matching (through high overall filler content) and maintained adhesion (through controlled distribution pattern).
2Strength
If primer layer is added to maintain adhesion with high filler content, then adhesive strength is improved, but manufacturing complexity increases
Solution Approach 1:
The patent extracts the primer layer from the structure by demonstrating that it is not needed when the insulating layer has the proper concentration gradient configuration. The gradient distribution of inorganic filler itself provides the necessary adhesion mechanism, eliminating the need for an additional primer layer and simplifying the overall structure.
Solution Approach 2:
The insulating layer performs the dual function of both insulation and adhesion through its concentration gradient structure. The gradient distribution of inorganic filler enables the layer to self-adhere to the metal layer without requiring external assistance from a primer layer, making the system self-sufficient.
3Length of moving object
If insulating layer thickness is reduced for thinner PCBs, then PCB thickness is improved, but insulation performance may deteriorate
Solution Approach 1:
The patent uses composite materials by combining resin with high content of inorganic filler (such as glass beads, glass flakes, or other ceramic fillers) in a gradient distribution. This composite structure enables the insulating layer to achieve high insulation performance and thermal expansion matching within a reduced thickness, allowing thinner PCBs without sacrificing reliability.
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 enables the production of thin printed circuit boards with enhanced adhesion between the insulating and metal layers, maintaining insulation functionality and preventing adhesive strength loss due to increased inorganic filler content, while eliminating the need for additional processing steps like primer layer formation.
Implementation Method 1
forming an insulating layer by drying the resin composite such that the inorganic filler is precipitated in the coated resin composite
Data Source
AI summary
A method of manufacturing an insulation film includes: coating a resin composite on a lower protective film, the resin composite including an inorganic filler dispersed therein; forming an insulating layer by drying the resin composite such that the inorganic filler is precipitated in the coated resin composite; and laminating an upper protective film on the insulating layer.