Printed Wiring Board Insulating Layer Peel Strength
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Solution Overview
Problem
The challenge in producing printed wiring boards is the reduction in peel strength between insulating and conductive layers due to the high content of inorganic fillers, which leads to cracks and circuit distortion caused by thermal expansion differences.
Innovation Solution
A method involving an adhesive sheet with a support that exhibits specific expansion characteristics during heating, where the support is heated under controlled conditions to maintain a maximum expansion rate of 0.9% or less and a difference in expansion rates of 0.5% or less, ensuring excellent peel strength even with high inorganic filler content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the content of inorganic filler such as silica particles in the resin composition is increased to form an insulating layer with a low thermal expansion coefficient, then thermal expansion difference between insulating layers and conductive layers is reduced, but peel strength between the formed insulating layer and conductive layer decreases
Solution Approach 1:
The invention changes the parameter of support expansion characteristics by controlling the maximum expansion rate (0.9% or less) and expansion rate difference (0.5% or less) during heating. This parameter control allows the support to compensate for the reduced peel strength caused by high inorganic filler content, thereby maintaining both low thermal expansion coefficient and sufficient peel strength.
Solution Approach 2:
The invention utilizes thermal expansion characteristics of the support to resolve the contradiction. By controlling the support's expansion behavior during heating (maximum expansion rate of 0.9% or less and expansion rate difference of 0.5% or less), the support compensates for the thermal expansion mismatch and maintains peel strength even when high content of inorganic filler is used in the resin composition.
2Productivity
If the number of stacked layers in the build-up printed wiring board is increased to meet demand for further densification of circuit wirings, then circuit density is improved, but occurrence of cracks and circuit distortion due to thermal expansion difference increases
Solution Approach 1:
The invention applies thermal expansion control by using a support with specific expansion characteristics (maximum expansion rate of 0.9% or less and expansion rate difference of 0.5% or less during heating). This control mechanism reduces thermal expansion differences between stacked layers, thereby preventing cracks and circuit distortion even when the number of stacked layers is increased to achieve higher circuit density.
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 forms an insulating layer with excellent peel strength after roughening treatment, maintaining high inorganic filler content without significant detachment, thus preventing cracks and distortion.
Implementation Method 1
when the support is heated under the following heating condition, the support satisfies the following conditions (TD1) and (TD2) in a TD direction thereof... a maximum expansion rate EATD (%) is 0.9% or less, and a difference between the maximum expansion rate EATD (%) and an expansion rate at the end of heating EBTD (%), EATD−EBTD, is 0.5% or less
Implementation Method 2
thermally curing the resin composition layer to form an insulating layer
Data Source
AI summary
Printed wiring boards, in which the insulating layer exhibits excellent peel strength with respect to a conductive layer after a roughening treatment, even when using a resin composition having a high content of inorganic filler, may be obtained by: (A) laminating, onto an internal layer substrate, an adhesive sheet which includes a support and a resin composition layer in contact with the support, so that the resin composition layer is in contact with the internal layer substrate; (B) thermally curing the resin composition layer to form an insulating layer; and (C) removing the support, when the support satisfies certain conditions (TD1) and (TD2) in a TD direction thereof when it is heated under specific heating conditions.