Adhesion to substrate materials Research and Development Department of Company J, a electronic materials manufacturer
High-speed, high-capacity PCB requirements
Adhesion improvement of low-dielectric substrates and copper
Company J manufactures printed wiring boards and other products for electronic equipment manufacturers, including those in the fields of communications and transportation equipment. As 5G communications and advanced autonomous driving technology advance, there has been an increasing demand for printed wiring boards capable of handling high-speed, large-volume data transmission. The R&D department began developing a new, high-performance printed wiring board, but was plagued by major challenges.
Challenges
Development began on both the board material and copper foil sides, but there was an issue with them peeling off easily...
To achieve high-speed, large-capacity data transmission, printed wiring boards with low transmission loss that can handle high frequencies are required. To achieve this, two elements were required: low dielectric constant materials used for the insulating layer of the board, and low surface roughness of the copper foil, which is the conductor. Therefore, the development team at Company J began to explore low dielectric constant board materials and the use of low-roughness copper foil.
Mr. A, who was the development team leader, looks back on the situation at that time as follows:
"Low-dielectric circuit board materials have lower adhesive properties compared to conventional epoxy resins, and it is known that conventional methods result in weak adhesion to copper foil. In addition, the use of low-roughness copper foil reduces the anchor effect caused by the unevenness of the copper foil. This further reduces adhesion to the circuit board material, making the copper foil more susceptible to peeling."
In order to improve adhesion, Mr. A and his development team tried using adhesives that were thought to be effective for low-dielectric substrate materials, and surface treatments such as applying a silane coupling agent to the surface of the low-coat copper foil. As a result, the peel strength was indeed improved, but the target performance could not be achieved.
The development team was beginning to get impatient as they were unable to find a way to achieve satisfactory adhesion between the low dielectric substrate material and the low-coat copper foil.
Key Challenges
High-speed, large-volume data transmission requires low-dielectric substrate materials and low-roughness copper foil.
Conventional copper foil surface treatments were also considered, but no method for successfully bonding low-dielectric material and low-roughness copper foil could be found.