PCB Adhesive Transparency via Low-Temp Curing
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Solution Overview
Problem
The existing methods for manufacturing printed circuit boards with visible circuits face issues due to the etiolating phenomenon in the adhesive layers caused by high temperature and pressure during lamination, leading to damage and loss of transparency.
Innovation Solution
A method involving a copper-clad laminate with specific adhesive and dielectric layers made of Epoxy-Acrylate and polyethylene terephthalate, where the lamination process is controlled with temperature and pressure to prevent the adhesive layers from flowing and hardening below 150°C, ensuring the transparency of the printed circuit board.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high temperature and high pressure force are applied during lamination to protect wiring layers, then the wiring layers are protected from damage, but the adhesive layers undergo etiolating phenomenon and lose transparency
Solution Approach 1:
The patent changes the temperature parameter of the lamination process by using a low-temperature curing adhesive layer that cures at temperatures not exceeding 150°C, replacing the conventional high-temperature lamination process. This parameter change allows the adhesive layer to maintain transparency while still achieving proper bonding and protecting the wiring layers.
Solution Approach 2:
The patent employs a composite material approach by using a specifically formulated low-temperature curing adhesive layer with controlled gel fraction (30-80%) and molecular weight characteristics. This composite adhesive formulation enables the material to achieve adequate bonding strength and protective function without requiring high temperature exposure that would cause etiolating and transparency loss.
2Strength
If high temperature is used during lamination to ensure adhesive bonding, then the adhesive layers bond properly, but the adhesive layers flow and harden improperly causing etiolating
Solution Approach 1:
The patent changes the temperature parameter by implementing a low-temperature curing process (≤150°C) with controlled time and pressure conditions. This parameter modification prevents the adhesive layer from flowing excessively or hardening improperly, maintaining both bonding strength and structural integrity without etiolating phenomenon.
Solution Approach 2:
The patent applies preliminary anti-action by pre-formulating the adhesive layer with specific properties (gel fraction 30-80%, controlled molecular weight) that prevent flow and improper hardening before the lamination process begins. This preliminary preparation ensures the adhesive maintains its shape and integrity throughout the bonding process without requiring high temperature that would cause deformation.
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
The method effectively prevents the etiolating phenomenon, maintaining the transparency and integrity of the printed circuit board by controlling the lamination conditions, ensuring the adhesive layers harden without flowing and adhering to the circuit components.
Implementation Method 1
a hardening temperature of the first adhesive layer 112 and a second adhesive layer 131 is lower than 150 degrees centigrade
Data Source
AI summary
A printed circuit board with circuit visible includes a wiring layer, a first adhesive layer, a first dielectric layer, and a cover film, which are stacked in described order, the wiring layer comprising at least one electrical contact pad. The cover film has at least one opening corresponding to the electrical contact pad. The cover film includes a second dielectric layer and a second adhesive layer. A flow initiation temperature of the first adhesive layer is in a range from 85 degrees centigrade to 90 degrees centigrade, and a hardening temperature of the first adhesive being lower than 150 degrees centigrade.