Flexible printed circuits use the same process and equipment conditions as rigid PCBs. In terms of processing, there is sheet-by-sheet processing: Sheet by Sheet, which is similar to the intermittent step-by-step processing of rigid PCBs, or roll-to-roll processing, which is the continuous processing of a roll of substrate. These two processes have their own advantages and disadvantages and are suitable for different production needs and product types.
What is Roll to Roll of Flex PCB processing?
Roll-to-roll (R2R) technology is a method of manufacturing whereby a flexible substrate roll material is continuously fed from one roll onto another. This allows for the embedding, coating, printing, or laminating of various applications. It is especially useful in industries that need to produce large quantities of flexible materials such as flexible PCB sheets, flexible solar panels, and wearable devices. R2R is the fastest and most cost-effective way to produce large-area flexible electronics.
The continuous production of large-scale flexible substrates is possible due to the uninterrupted transport of flexible substrates in rolls. Continuous production is a high-efficiency production method that's suitable for large-scale production. The production costs are reduced because it reduces labor and material switching costs. The consistency and uniformity of the product is maintained by continuous production. The roll-to-roll process is a challenging one, as it can require sophisticated tension control systems and registration systems to achieve dimensional accuracy.
Process flow:
Rolled flexible substrates (such as polyimide or polyester film) are used to make circuit patterns on the substrate by methods such as photolithography or printing. The excess copper is then removed by a chemical etching process to form a circuit pattern. The circuit is then surface finished (such as gold plating, tin spraying, etc.) to increase conductivity and oxidation resistance. Finally, a protective film is covered on the surface of the flexible printed circuit to provide mechanical protection and electrical insulation. After the flexible printed circuit is tested, it is wound into a roll.
Advantages:
Low production costs, good consistency, and low material waste.
Disadvantages:
Large initial investment and high equipment requirements. Not suitable for the production of small batches.
Summary:
The R2R process is highly efficient and cost-effective, but its use in double-sided flex PCB sheets and multi-layer flex PCB production is severely limited. R2R is not suited for the alignment and interlayer connections of double-sided flex PCB, lamination and heat treatments of multi-layer PCB, or other processes. Therefore, although it can be applied to some special designs and optimizations, the R2R process is usually more suitable for single-sided flex PCBs and simple double-sided flex PCBs.
What is sheet by sheet of Flex PCB processing?
Sheet by Sheet (S2S) production process means that when manufacturing a Flexible printed circuit, each step of the process is processed for a single piece of flexible substrate.
Process flow:
The flexible substrate is first cut into a piece of a specified size. Next, the circuit pattern will be transferred onto the substrate by exposure and development. To form the circuit, the excess copper must be removed using a chemical etching procedure. The hole wall or circuit pattern is surface-treated (such as by ENIG, gold plating, spraying tin, etc.). To increase conductivity and resistance to oxidation. A protective film is then applied to the surface of the board for mechanical protection and insulation. The finished flexible printed circuit is then tested, separated, and cut.
Advantages:
Suitable for small-batch production of multiple varieties. Low equipment investment. Quality control measures can be implemented more easily for each substrate. Precision and control of dimensional stability for each layer are improved. If there are any defects or problems during the flexible PCB process, the sheet that is causing the problem can be discarded. This reduces material waste.
Disadvantages:
Low production efficiency, not suitable for mass production. Relatively high production cost. Since each substrate must be processed individually, the production speed is slower compared to R2R.
Summary:
S2S is widely used in the production of Flexible PCB sheets, including multi-layer flex PCBs, sculpture flex circuits, Dual access flex PCBs, etc. It is suitable for applications that require high precision and complex layer structures, such as aerospace, automotive, and high-performance computing devices.
The choice of R2R or Sheet-by-sheet process mainly depends on the production scale, product type, and market demand. For flex PCBs with high mass production and high consistency requirements, the R2R process is more suitable; while for products with high variety and small batch Flex PCBs requiring higher flexibility, the Sheet by Sheet process is more suitable. Please contact us to learn more about the production process of flexible printed circuits.
Flex Plus (Xiamen) Co., Ltd. is a manufacturer specializing in the production of flexible circuit boards. The products cover single-sided, double-sided, multilayer flex PCB, rigid-flex PCB sheet, split and dual access (back bare) flex PCB, sculpturer flex circuit boards, and other types of flexible circuit boards, which can meet the needs of customers for all kinds of products.
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