Multilayer PCB via formation using conductive paste printing
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Solution Overview
Problem
Conventional multilayer printed wiring boards face challenges in achieving high density and reducing manufacturing costs due to increased signal speeds, thermal expansion coefficient mismatches, and complex manufacturing processes involving liquid crystal polymer insulating layers and conductive vias.
Innovation Solution
A manufacturing method involving the use of single-sided and double-sided metal-foiled laminate sheets with conductive pastes to create bottomed via holes and step via holes, allowing for the lamination of two wiring substrates to form a multilayer printed wiring board with three interconnected wiring layers, reducing material and process complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If liquid crystal polymer is used as an insulating layer to reduce dielectric loss, then transmission loss is reduced, but reliability deteriorates due to high thermal expansion coefficient
Solution Approach 1:
The patent divides the insulating layer into multiple thin layers (first insulating layer, second insulating layer, third insulating layer) rather than using a single thick liquid crystal polymer layer. This segmentation allows each thin layer to have controlled thermal expansion while collectively achieving the desired dielectric properties and reducing overall transmission loss.
Solution Approach 2:
The patent uses a composite structure combining multiple different insulating materials (each with different dielectric constants and thermal expansion coefficients) in a stacked configuration. This composite approach allows optimization of both dielectric loss and thermal expansion characteristics by selecting materials with complementary properties.
2Reliability
If plated throughholes are used for inter-layer connection, then connection reliability is improved, but manufacturing cost and complexity increase
Solution Approach 1:
The patent extracts the plating process from the manufacturing flow and replaces it with a printing process for forming conductive patterns. This eliminates the complex plating operations (electroplating, chemical plating, rinsing, drying) while maintaining connection functionality through printed conductive paste layers.
Solution Approach 2:
The patent replaces the electrochemical plating system with a printing system that deposits conductive paste directly onto the insulating layers. This substitution simplifies the manufacturing process by eliminating plating equipment and associated chemical processes while achieving the same inter-layer connection function.
3Productivity
If the number of wiring substrates to be laminated is increased to achieve high density, then connection density is improved, but positional deviation increases and manufacturing difficulty increases
Solution Approach 1:
The patent merges multiple wiring substrate layers into a single integrated structure where conductive patterns are printed directly on each insulating layer. This consolidation reduces the number of separate lamination steps required while maintaining high connection density, thereby minimizing cumulative positional deviations.
Solution Approach 2:
The patent performs preliminary positioning and alignment of conductive patterns during the printing process itself, rather than relying on post-lamination alignment. This preliminary action ensures precise positional accuracy is achieved before lamination occurs, preventing cumulative deviations.
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 simplifies the manufacturing process, reduces material requirements, and enhances yield by avoiding positional deviations, thereby achieving high-density multilayer printed wiring boards at a lower cost.
Implementation Method 1
an adhesive protective film having a weak adhesive layer formed on one side thereof is attached to a single-sided metal-foiled laminate sheet
Implementation Method 2
filling a conductive paste into the bottomed via hole by a printing method
Implementation Method 3
causing a part of the conductive paste filled in the bottomed via hole to protrude from the first insulating resin film
Implementation Method 4
the laminated first and second wiring substrates are heated to be integrated with each other
Data Source
AI summary
A wiring substrate is manufactured by attaching an adhesive protective film to a metal-foiled laminate sheet, forming bottomed via holes by partially removing the film and an insulating film, filling conductive pastes into the holes, and peeling the film. A wiring substrate is manufactured by forming an adhesive protective layer so as to cover a patterned metal foil on a metal-foiled laminate sheet, forming bottomed step via holes by partially removing the layer and an insulating film, filling conductive pastes into the holes, and peeling off a protective film. The wiring substrate and the second wiring substrate are laminated in such a way that protruding parts of the pastes come into contact with respective protruding parts of the pastes.