Multilayer PCB via interconnects using conductive paste
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Solution Overview
Problem
The existing methods for manufacturing printed circuit boards face challenges such as significant adhesive shrinkage during curing, leading to stress and unreliable interconnections, and the costly and time-consuming process of plating through-holes with copper, which complicates quick assembly and alignment.
Innovation Solution
The method involves forming countersinks and holes in sub-assemblies, metalizing them, applying conductive paste-filled vias, and laminating these sub-assemblies to create a multilayer printed circuit board with Z-axis interconnects, allowing for stress-free bonding and reduced assembly costs through parallel processing in one or two lamination cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper plating is used to interconnect circuit layer pairs, then reliable electronic interconnection is achieved, but manufacturing complexity and cost increase significantly
Solution Approach 1:
The invention changes the material parameter from copper to conductive paste, and changes the formation method from electroplating to screen printing. This parameter change simplifies the manufacturing process while maintaining electrical conductivity functionality, directly resolving the contradiction between reliability and manufacturing complexity
Solution Approach 2:
The invention replaces the expensive and time-consuming copper plating process with a cheaper conductive paste application method. The conductive paste serves as a temporary but functional interconnection medium that achieves the desired electrical connection without requiring the complex and costly copper plating process
2Reliability
If copper plating process is used for through-holes, then conductive interconnections are formed, but production time and cost increase
Solution Approach 1:
The invention changes the material from copper to conductive paste and changes the application method from electroplating to screen printing. This parameter change dramatically reduces production time while maintaining the conductive interconnection function, directly addressing the productivity issue
Solution Approach 2:
The conductive paste is applied to the circuit board surface before final assembly, allowing interconnections to be prepared in advance. This preliminary action eliminates the need for time-consuming copper plating during the assembly process, thereby improving production speed
3Strength
If adhesive curing process is used to bond circuit layers, then permanent bonding is achieved, but significant stress is introduced into the structure
Solution Approach 1:
The invention uses a composite structure combining rigid circuit board layers with flexible adhesive layers. This composite material approach allows the rigid parts to provide structural strength while the flexible adhesive layers accommodate dimensional changes, reducing internal stress while maintaining bonding strength
Solution Approach 2:
The invention changes the adhesive formulation parameters to reduce shrinkage during curing. By modifying the chemical composition and curing characteristics of the adhesive, the patent achieves permanent bonding with significantly reduced stress introduction into the overall structure
4Manufacturing precision
If through-hole drilling and plating are performed sequentially, then precise interconnections are achieved, but assembly time and cost increase
Solution Approach 1:
The invention merges the interconnection formation process with the circuit board manufacturing process itself. By applying conductive paste during the same manufacturing cycle as circuit trace formation, the patent eliminates separate drilling and plating steps, achieving precise interconnections without time loss
Solution Approach 2:
The conductive paste interconnections are formed preliminarily during circuit board manufacturing, before final assembly. This preliminary formation of interconnections eliminates the need for subsequent time-consuming drilling and plating operations, maintaining precision while reducing overall assembly time
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 multilayer printed circuit boards with enhanced functionality and reduced assembly costs by eliminating the need for copper plating and minimizing stress-related issues, while allowing for faster and more reliable interconnections.
Implementation Method 1
curing the resulting circuit board structure
Implementation Method 2
fabricating an adhesive (or a prepreg or a bond ply), stacking the circuit layer pairs and the adhesives in a press, curing the resulting circuit board structure
Implementation Method 3
filling at least one conductive paste into the at least one via formed in the lamination adhesive
Implementation Method 4
metalizing the at least one hole and the at least one countersink to metalize the at least one hole and the at least one countersink
Data Source
AI summary
Methods of manufacturing at least a portion of a printed circuit board. The circuit board is formed to include a plurality of sub-assemblies, each of the sub-assemblies including a plurality of circuit layers and having at least one countersink and at least one hole, the countersink having a first diameter and a first depth from a first side of at least one of the sub-assemblies and into the at least one sub-assembly, the hole having a second diameter smaller than the first diameter and a second depth longer than the first depth from the first side of the at least one sub-assembly and into the at least one sub-assembly at the countersink; a metal metalized within the hole and the countersink; a lamination adhesive interposed between one and a corresponding one of the sub-assemblies and having at least one via formed therethrough; and a counter paste filled within the via.