Multilayer PCB Adhesive Thickness Control via Edge Spacers
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Solution Overview
Problem
In the manufacturing of multilayer printed wiring boards, the thermocompression bonding process often results in variations in the thickness of the adhesive layer, affecting the impedance characteristics due to deformation and molten adhesive entering circuit gaps, leading to deviations from the designed impedance values.
Innovation Solution
A method involving the use of spacers with a predetermined thickness is introduced, arranged along the outer edges of the circuit regions, creating a space between the adhesive layer and the spacer to maintain the adhesive layer's thickness and prevent deformation during thermocompression bonding, ensuring consistent impedance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thermocompression bonding is performed with an adhesive layer, then interlayer adhesion is achieved, but the adhesive layer deforms and thickness varies, affecting impedance characteristics
Solution Approach 1:
The patent changes the physical state parameters of the adhesive layer by controlling temperature and pressure during thermocompression bonding. By optimizing these parameters, the adhesive layer achieves proper bonding while minimizing deformation and thickness variation, thus resolving the contradiction between adhesion strength and thickness precision.
Solution Approach 2:
The adhesive layer undergoes phase transition from solid to molten state during thermocompression bonding, then solidifies after cooling. This phase transition enables the adhesive to flow and fill gaps for good adhesion, while controlled cooling allows the layer to solidify with minimal thickness variation, addressing both adhesion and precision requirements.
2Strength
If pressure is applied under high temperature in thermocompression bonding, then bonding is achieved, but the adhesive layer deforms and thickness deviates from target design value
Solution Approach 1:
The patent applies preliminary anti-action by pre-positioning spacers or using fiducial marks to define the exact bonding area and pressure distribution. This preliminary setup prevents excessive deformation of the adhesive layer during bonding, ensuring thickness remains close to the target design value while still achieving proper bonding.
Solution Approach 2:
The patent employs feedback mechanisms through thickness measurement and control systems that monitor the adhesive layer thickness during or after bonding. Based on this feedback, bonding parameters such as pressure and temperature are adjusted to compensate for deformation, maintaining thickness precision while achieving adequate bonding strength.
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 production of multilayer printed wiring boards with impedance characteristics as initially designed, by maintaining the adhesive layer's thickness and preventing changes in the distance between signal lines and adjacent conductive layers, thus ensuring reliable transmission path performance.
Implementation Method 1
when interlayer adhesion is performed by thermocompression bonding with an adhesive layer, the adhesive layer melts
Implementation Method 2
laminating the first wiring board and the second wiring board for thermocompression bonding
Data Source
AI summary
A method for manufacturing a multilayer printed wiring board includes: preparing a first wiring board that includes a circuit region formed with one or more signal lines on a main surface of a first insulating substrate; preparing a second wiring board that includes an electrically conductive layer on a main surface of a second insulating substrate; disposing a spacer at a position spaced apart from an outer edge of the circuit region by a predetermined distance along at least a part of the outer edge; disposing an adhesive layer on the circuit region so that a space is provided between the adhesive layer and the spacer; and laminating the first wiring board and the second wiring board for thermocompression bonding.