FPC flexible printed circuit board, also known as "flexible board" in English, is a highly reliable and excellent flexible printed circuit made of flexible insulation substrates such as polyimide or polyester film. It has the characteristics of high wiring density, light weight, thin thickness, and good bendability. Flexible printed circuit boards are also divided into single-sided, double-sided, and multi-layer boards.

Flexible circuit boards are mainly used in the connection parts of electronic products. Its advantage is that all lines are fully configured. Eliminate the need for extra wiring connectors; It can improve softness. Strengthen the assembly of three-dimensional space within a more limited space; It can effectively reduce the volume of the product. Enhance the convenience of carrying; It can also reduce the weight of the final product.

Scope of testing

The scope of this standard includes single-sided, double-sided, and multi-layer boards for flexible circuits. The flexible circuit board referred to in this standard refers to single, double, and multi-layer flexible copper foil substrates based on polyimide (PI) or polyester (PET), including adhesive (3L-FCCL) and adhesive free (2L-FCCL) flexible copper foil substrates.

Test purpose

The purpose of this standard is to establish a general rule for determining the appearance quality of flexible circuit boards, which serves as the basis for determining whether to accept or reject the appearance quality of flexible circuit board products between Tianpai Company and suppliers. This will help improve manufacturing technology and reduce resource waste and environmental pollution caused by unnecessary scrapping.

test method

This specification specifiesThe main inspection methods and tools used in the experiment are visual inspection, magnifying glass, and ruler. If necessary, other applicable testing instruments or equipment may be used for inspection.

Basic testing standards

1. Appearance of substrate film surface:

The allowable defect range for the appearance of the substrate film surface where the conductor does not exist is listed in the table. No other bumps, creases, wrinkles, or foreign objects that may affect the use are allowed.

2. Appearance of covering layer:

Defects in the appearance of the covering film and coating: allowable range, no bumps, creases, folds, or delamination that affect use are allowed.

3. Deviation between connection disk and overlay:

The deviation e between the connecting plate and the covering layer is allowed to be within ± 0.3mm when the external dimensions are less than 100mm, and within ± 0.3% of the external dimensions when the external dimensions are above 100mm.

4. Adhesive and coating flow infiltration:

The flow infiltration degree f of the adhesive and the coating should be less than 0.2mm. However, at the connection plate, with the addition of cover layer deviation and punching deviation, the minimum ring width g must be ≥ 0.05mm

5. Color change:

The conductor under the covering layer must still meet the requirements of voltage resistance, bending resistance, bending resistance, and welding resistance after undergoing a humidity resistance test at a temperature of 40 ℃, humidity of 90%, and 96 hours.

6. Leakage of coating layer:

The leakage of the coating layer should be tested according to the solderability requirements, and no tin should be stuck on the conductor of the leakage part of the coating layer.

7. Poor electroplating bonding:

The coating is not allowed to have delamination. The width W1 and length L of the coating joint are poor, and the width W of the processed conductor is not allowed. Moreover, the poor bonding of the coating shall not damage the reliability of the contact area.

The above is the testing methods and standards for FPC flexible circuit boards compiled by the editor. We hope it is helpful to everyone. If there are still any unclear areas, please contact our customer service for answers.