Multilayer PCB Alignment via Anisotropic Conductive Adhesive
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Solution Overview
Problem
The existing methods for manufacturing multilayer printed circuit boards face challenges in aligning and connecting multiple electrically conductive layers due to variations in environmental conditions, leading to issues with shrinkage and expansion, which affect the precision and reliability of the PCBs.
Innovation Solution
A method involving the use of anisotropically conductive adhesive layers and through holes in the dielectric layers to align and connect multiple circuit substrates during lamination, ensuring precise electrical contact and alignment without the need for multi-step electroplating, thereby reducing misalignment and deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple electrically conductive layers are laminated together in multi-step processes, then the PCB achieves high-density inter-connectability, but alignment precision deteriorates due to shrinkage and expansion from environmental factors
Solution Approach 1:
The patent applies preliminary action by pre-forming through holes in each circuit substrate before lamination. These through holes are positioned in advance to ensure precise alignment when substrates are stacked, preventing misalignment issues that would occur if holes were formed after assembly. This preliminary preparation of alignment features resolves the contradiction by establishing precise registration points before the lamination process begins.
Solution Approach 2:
The patent uses anisotropically conductive adhesive as an intermediary material between circuit substrates. This adhesive layer serves multiple functions: it bonds the substrates together while its anisotropic conductivity allows electrical connection only in specific directions (through the holes), preventing haphazard conductivity. The intermediary adhesive layer accommodates minor dimensional variations and shrinkage/expansion differences between layers, maintaining alignment precision despite environmental factors.
2Reliability
If multi-step electroplating is used to connect conductive layers, then electrical connectivity is achieved, but process complexity and time increase
Solution Approach 1:
The patent extracts and eliminates the complex multi-step electroplating process by using anisotropically conductive adhesive instead. The adhesive material inherently provides both mechanical bonding and electrical connectivity through its conductive particles, removing the need for separate electroplating operations. This extraction of the electroplating function simplifies the overall manufacturing process while maintaining reliable electrical connections between layers.
Solution Approach 2:
The patent merges the functions of mechanical adhesion and electrical connection into a single anisotropically conductive adhesive layer. Instead of using separate adhesive and conductive layers (or requiring electroplating for conductivity), the adhesive material itself provides both bonding strength and controlled electrical pathways through its anisotropic conductive properties. This merging reduces process steps and simplifies manufacturing while ensuring reliable connectivity.
3Ease of manufacture
If conventional lamination processes are used, then manufacturing is straightforward, but deformation and misalignment occur due to shrinkage and expansion
Solution Approach 1:
The patent applies parameter changes by utilizing the anisotropic conductivity parameter of the adhesive material. This material has different conductivity properties in different directions: it is conductive in the through-hole direction (vertical) but insulating in the planar direction (horizontal). This parameter differentiation allows the adhesive to provide electrical connection only where needed (through aligned holes) while preventing unwanted conductivity between adjacent traces, thereby maintaining alignment precision even with conventional lamination processes.
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 simplifies the manufacturing process, improves alignment precision, and ensures reliable electrical connectivity between layers, reducing the risk of haphazard conductivity and deformation issues.
Implementation Method 1
a first anisotropically conductive adhesive layer 141 is formed on one of the second dielectric layer 113 and the fourth dielectric layer 123... the first anisotropically conductive adhesive layer 141... electrically connect the first conductive terminal 1111 and the second conductive terminal 1211
Data Source
AI summary
An exemplary multilayer printed circuit board includes a first circuit substrate, a third circuit substrate, a second circuit substrate between the first and third circuit substrates, a first anisotropically conductive adhesive layer between the first and second circuit substrates, and a second anisotropically conductive adhesive layer between the second and third circuit substrates. The first circuit substrate includes a first conductive terminal and a first through hole. The second circuit substrate includes a second conductive terminal and two through holes (i.e. second and third through holes). The third circuit substrate includes a third conductive terminal and a fourth through hole. The first anisotropically conductive adhesive layer fills the first and third through holes to electrically connect the first and second conductive terminals. The second anisotropically conductive adhesive layer fills the second and fourth through holes to electrically connect the second and third conductive terminals.