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The market share of FPC circuit board has been extended as consumer electronic products continue to develop towards miniaturization and lightness. Engineers have designed many flexible assembly products using the bendable and flexural characteristics of flexible FPC boards. FPC flexible circuit board bending is a common processing technology in the electronics industry, which requires not only a high degree of professional knowledge and skills, but also some skills to ensure the quality and effect of the bending process.
FPC circuit board
FPC bending test simulates the bending effect that FPC is subjected to in the actual use environment to evaluate the quality and performance of FPC circuit boards. Through the bending test, the ability of FPC circuit boards to withstand bending deformation during their service life can be judged, thereby judging their reliability, and it can also reflect the process quality of FPC. This is crucial for designers, because only through the bending test can the designed FPC circuit board be guaranteed to withstand the test of long-term use and meet the reliability requirements of the product.
Flexibility is the most obvious advantage of flex PCB, but we should maintain a certain amplitude during use, not just bending at will, so what should we pay attention to when bending? First of all, FPC cannot be bent at will.
1. Although FPC can be bent, if it is bent 180°, this may damage the copper wire and cause an open circuit or short circuit.
2. Most ink-type protective layers are not resistant to bending, such as text/silk screen, marking, solder mask, etc. Bending actions of more than 90° are strictly prohibited during assembly.
3. The corners of the FPC shape are easy to tear during assembly, so users are reminded to pay attention.
4. The exposed part of the FPC is surface-plated, such as gold plating/gold plating, etc., and the focus is on preventing oxidation. This area is not suitable for bending.
5. Although the gold finger plug-in area has a reinforcing rib design, it is still not suitable for bending in this area. Special attention should be paid to the assembly process.
6. Do not bend directly in the through-hole area of the FPC.
FPC circuit board bending design
1. Appropriate bending angle
In the bending process of the FPC flexible circuit board,the choice of bending angle is very important. The appropriate bending angle can avoid the stretching or compression of the circuit board, thereby reducing the stress and deformation of the circuit board. Generally speaking, the bending angle should be as large as possible as possible. The bending radius of the board. At the same time, avoid excessive bending angles to avoid circuit board breakage or circuit damage. Therefore, when performing bending operations, it is necessary to select a suitable bending angle according to the specific situation.
2. Appropriate circuit layout
When designing FPC flexible circuit boards, the layout of the circuits is also one of the key factors affecting bending. Reasonable circuit layout can minimize stress concentration at the bends of the circuits and improve the bending quality of the circuit boards. To achieve this goal, the layout of the circuits should avoid 90-degree angles as much as possible, and a gentle arc should be selected. In addition, attention should be paid to the spacing between the circuits to avoid interference and damage between the circuits.
3. Choose a suitable bending process
Choosing a suitable bending process is also very important for the quality and stability of FPC flexible circuit boards.Commonly used bending processes are manual bending and mechanical bending. Manual bending is suitable for some simple bending operations, but for complex bending tasks, mechanical bending is more reliable and accurate. When choosing a bending process, factors such as the material of the circuit board, the layout of the circuits, and the bending angle need to be considered to ensure that the selected process is most suitable for specific bending needs.
4. Use high-quality tools
When bending FPC flexible circuit boards, it is also very important to use high-quality tools. High-quality tools can provide accurate bending force and angle, reducing the risk of circuit board damage. Commonly used tools include bending molds and positioning fixtures. The bending mold should have a smooth surface and a suitable bending radius to ensure the smooth flow of the circuit board during the bending process. The positioning fixture can stably fix the circuit board and provide additional support and protection during the bending process.
5. The right bending angle, proper circuit layout, selection of the right bending process and the use of high-quality tools will help operators easily complete the bending process and ensure the integrity and stability of the circuit board. By following these guidelines, production efficiency and product quality can be improved with half the effort to meet market needs.
FPC bending test method
Depending on the different bending indicators and requirements, FPC bending tests can be tested in a variety of ways. Below, iPCB introduces two common test methods, including manual bending test and mechanical bending test.
1. Manual bending test
The manual bending test is a relatively simple and intuitive test method, which is suitable for preliminary screening of samples and evaluation of their flexibility. During the test, the FPC is fixed at one end point, and then it is manually bent a certain number of times and angles, and the FPC is observed to see if it breaks, cracks, or changes in resistance, in order to determine its quality and reliability.
2. Mechanical bending test
Mechanical bending test is a more accurate and standardized test method, which is widely used in a large number of FPC bending test scenarios. Common mechanical testing instruments include bending testers, bending durability testers, etc. Mechanical bending tests usually set parameters such as bending angle, speed, and number of times according to specific requirements, and monitor key indicators such as resistance change and tensile strength of the FPC during the test to evaluate its bending reliability.
Standards for FPC bending test
Internationally, a series of standards for FPC circuit board bending tests are widely adopted, such as IPC-2223C, JIS C6481, MIL-STD-2217, etc. These standards specify the test methods, test conditions, and test requirements for FPC during the bending test, ensuring the comparability and reliability of the test results. These standards mainly include the following:
1. Requirements for bending angle and bending radius: Designers need to select appropriate bending angle and bending radius according to the actual use environment and product requirements to ensure that the FPC can withstand bending deformation without damage during its service life.
2. Requirements for bending speed and number of bending times: By setting standard bending speed and number of bending times, the bending frequency and speed of FPC in actual use can be simulated to evaluate its durability and reliability.
3. Requirements for performance evaluation after bending: including changes in FPC resistance, changes in conductive performance, reliability of solder joints, etc. By detecting these key indicators, it can be determined whether the FPC can withstand use after bending deformation.
The formulation and implementation of FPC PCB bending test standards play a vital role in ensuring the stability and reliability of FPC flexible circuit boards. By reasonably selecting test methods and strictly implementing standard requirements, the bending reliability and service life of FPC circuit boards can be evaluated, providing strong guarantees for product design and manufacturing. At the same time, the formulation of unified testing standards will also help improve the quality level and market competitiveness of the entire industry, and promote the further improvement and development of FPC circuit board technology.