Innovative Semi-Additive Process Technology from GS Supports PCB Line Spacing Down to 10 microns

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GS Swiss PCB has been at the forefront of advancing printed circuit board (PCB) manufacturing technology to meet the growing demands of miniaturization in electronics. Recognizing the limitations of traditional subtractive methods, which are restricted to lines and spaces of around 30 micrometers, GS Swiss PCB began developing Semi-Additive Process (SAP) technology in 2019 and invested heavily in state-of-the-art equipment and cleanroom facilities. While modified Semi-Additive Process (mSAP) technology can handle line and space widths from 60 down to 20 micrometers, SAP pushes the limits even further, enabling conductor lines and spaces as small as 10 micrometers and below for both flexible and rigid PCBs.

Building on these efforts, the company achieved a major milestone in spring 2024 by commencing serial production of flexible PCBs using SAP technology. This breakthrough not only improves yields for highly miniaturized designs but also positions GS Swiss PCB to meet evolving customer needs and drive innovation in next-generation electronics. By mastering SAP, the company is setting new standards in PCB manufacturing precision and efficiency.

How is the Manufacturing Process Carried Out?

1. Subtractive Technology: This traditional method begins with a fully copper-clad laminate. A structured photoresist covers the desired copper structure, protecting the underlying copper during the etching process. After stripping the photoresist, only the intended copper traces remain.

Cross-Section Characteristics of Subtractive Technology: The traces have a trapezoidal cross-section because the etching process removes copper from the top and sides of the traces. This leads to wider traces at the base than at the top.

2. Modified Semi-Additive Process (mSAP): mSAP starts with a laminate that has a very thin copper layer, which is covered with a photoresist to define the circuit pattern. Additional copper is plated onto the exposed areas to build up the desired traces. After stripping the photoresist, the thin copper layer between the tracks is etched away, leaving the desired copper structure.

Cross-Section Characteristics of mSAP Technology: The traces have a more rectangular cross-section compared to the subtractive process.

3. Semi-Additive Process (SAP): SAP uses a non-conductive substrate with an extremely thin copper layer (less than 1 μm) plated onto it. Copper is then built up only in the open areas defined by a precise photoresist pattern to form the desired structure. After stripping the photoresist, the very thin copper layer remaining between the tracks is etched away using flash etching, leaving the desired copper pattern.

Cross-Section Characteristics of SAP Technology: The traces have nearly perfect rectangular cross-sections with sharp and defined edges. SAP offers the best control over dimensions and trace geometry among the three manufacturing methods.

Process Steps: Subtractive – mSAP - SAP

Advantages of mSAP and SAP Technologies

Fine Line Capability: mSAP and, to an even greater extent, SAP technology enable the manufacturing of dense patterns that are unachievable with conventional subtractive methods. This advancement allows for the creation of highly miniaturized products that were previously not possible.

Improved Performance: SAP technology provides exceptional control over trace geometry and spacing, resulting in nearly rectangular cross-sections and smooth surfaces. This precision ensures consistent electrical characteristics across the board and minimizes parasitic effects, which are crucial for optimal performance and signal integrity at high frequencies.

Versatility in Design: mSAP and SAP technologies provide greater flexibility in circuit design, allowing for innovative and custom solutions tailored to specific applications. This can be a significant competitive advantage in developing new products.

Environmental Benefits: These technologies often require fewer materials and generate less waste compared to traditional subtractive processes, contributing to more sustainable manufacturing practices.

Applications of mSAP and SAP Technologies

mSAP and SAP technology are crucial for applications requiring extreme miniaturization, such as IC substrates and smartphones. These technologies are also essential for manufacturing products that need high signal density for superior resolution and precise imaging, like advanced ultrasound and MRI devices. In 5G infrastructure components, the precise shapes of conductors ensure the undistorted high-frequency signals necessary for advanced telecommunications.

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