Multilayer PCB Insulating Layer for Small Laser-Drilled Vias
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Solution Overview
Problem
Existing methods for manufacturing multi-layer printed wiring boards face challenges in achieving smaller via hole diameters while maintaining the heat resistance of the electrical insulating layer, particularly when using a release substrate with a glass transition point and a heat-curable resin composition layer with a high volatile component content.
Innovation Solution
The method involves forming a heat-curable resin composition layer with a volatile component content of no more than 7.0 wt% and a thickness of no more than 25 µm, using a release substrate at least 80 µm thick, and curing it at a temperature above the glass transition point of the release substrate material, followed by laser processing to create a small diameter hole for the via, thereby reducing the via diameter and maintaining heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a release substrate at least 80 µm thick is used to form small diameter via holes by laser processing, then the via hole diameter is reduced, but the heat resistance of the electrical insulating layer drops causing swelling during heating
Solution Approach 1:
The patent applies parameter changes by strictly controlling the volatile component content (≤7.0 wt%) and thickness (≤25 µm) of the heat-curable resin composition layer, and controlling the curing temperature to be at or above the glass transition point of the release substrate material. These parameter adjustments enable the formation of small diameter via holes while preventing the drop in heat resistance of the electrical insulating layer.
Solution Approach 2:
The patent uses a composite structure consisting of the release substrate, heat-curable resin composition layer, and electrical insulating layer. By carefully selecting and combining these materials with specific properties (release substrate with glass transition point, resin composition with controlled volatile content), the patent achieves both small via hole diameter and maintained heat resistance.
2Ease of manufacture
If the volatile component content in the heat-curable resin composition layer is high, then the resin cures easily, but the heat resistance of the electrical insulating layer drops during heating
Solution Approach 1:
The patent applies parameter changes by setting the volatile component content to no more than 7.0 wt% and the thickness to no more than 25 µm. This controlled reduction in volatile components prevents excessive outgassing during heating while still allowing proper curing of the resin composition layer, thereby maintaining heat resistance during soldering processes.
3Reliability
If the thickness of the heat-curable resin composition layer is increased, then the electrical insulating properties are improved, but the via hole diameter becomes larger
Solution Approach 1:
The patent applies parameter changes by optimizing the thickness of the heat-curable resin composition layer to no more than 25 µm. This controlled thickness enables the formation of small diameter via holes through laser processing while still providing adequate electrical insulating properties when combined with the release substrate structure.
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 allows for the manufacture of small, high-density multi-layer printed wiring boards with improved heat resistance and reduced swelling during soldering, by forming a via with a small diameter while preventing a drop in the electrical insulating layer's heat resistance.
Implementation Method 1
a hole for a via is formed in the electrical insulating layer by irradiating a laser from above the release substrate
Implementation Method 2
an electrical insulating layer - to which the release substrate has been adhered by curing the heat-curable resin composition layer, to which the release substrate is adhered, at a temperature at or above the glass transition point of the material of the release substrate
Data Source
AI summary
The present invention enables the manufacture of a small, high-density multi-layer printed wiring board. The method for manufacturing a multi-layer printed wiring board according to the present invention includes; a step for forming an electrical insulating layer by heating a laminate provided with a substrate, a heat-curable resin composition layer provided on the substrate, and a release substrate provided on the heat-curable resin composition layer, thereby curing the heat-curable resin composition layer; and a step for forming a hole for a via in the electrical insulating layer by irradiating a laser from above the release substrate. Furthermore, in the present invention, the release substrate is at least 80 µm thick and is formed using a material having a glass transition point, the heat-curable resin composition layer contains no more than 7.0 wt% of a volatile component and is no more than 25 µm thick, and the curing of the heat-curable resin composition layer occurs at a temperature that is equal to or greater than the glass transition point of the material of the release substrate.