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1. What is the difference between FPC solder mask and cover layer?
When designing flexible circuit boards, have you encountered troubles in choosing solder masks and overlays? The solder mask and the cover layer have the same basic insulation function. Do you know the difference between the solder mask and the cover layer?
When designing flexible circuit boards, have you encountered troubles in choosing solder masks and overlays? The solder mask and the cover layer have the same basic insulation function. Do you know the difference between the solder mask and the cover layer? Can the solder mask and the cover layer be overlapped for insulation? Do you think that the flexible solder mask is the same as the rigid printed circuit solder mask?
1) Design: In fact, coverlay is widely used in flexible circuit boards. Because most FPCs need to add PI/FR4 reinforcement and EMI shielding layer. However, if there are BGA pads and a dense solder mask opening area, it will limit the minimum size of the opening and the smallest material net, which can then be kept between adjacent openings.
I want to share with you the cover layer and solder mask that the FPCB covers together. Cover the cover layer first, and then slightly overlap the solder mask to cover the cover layer to prevent any gaps in the combined layer. This design has higher requirements for our production to ensure your function and reliable design.
2) Thickness: Why choose to use green solder resist instead of covering layer? The normal cover layer thickness is 27.5/50um. The thickness of the solder mask is 8/12um. Because customers need ultra-thin flexible PCB. Then, we recommend that customers use solder mask instead of overlay.
3) Color: The most popular cover film color is yellow, we usually prepare yellow, white and black cover films in stock. Solder masks are available in green, black, white, yellow and other colors. Please note that FPC solder mask is completely different from PCB. The cost of FPC solder mask is much higher than that of PCB, because the bending resistance and high temperature resistance of flexible circuit board solder mask are better than PCB.
2. Test methods and standards for FPC soft boards
The purpose of FPC soft board testing is to establish a general rule for the appearance and quality of FPC soft boards. The basis for judging the appearance quality of FPC soft board products is allowed to reject, which will help to improve manufacturing technology and reduce the waste of resources caused by unnecessary scrap And environmental pollution.
Text label: FPC soft board, FPC test method, FPC test standard
FPC soft board refers to single, double and multi-layer flexible copper foil substrates with polyimide (PI) or polyester (PET) as the base material, including adhesive and non-adhesive flexible copper foil substrates. The purpose of FPC soft board testing is to establish a general rule for the appearance and quality of FPC soft boards. The basis for judging the appearance quality of FPC soft board products is allowed to reject, which will help to improve manufacturing technology and reduce the waste of resources caused by unnecessary scrap And environmental pollution. Test method The test method uses visual inspection, magnifying glass, and ruler as the main inspection methods and tools. If necessary, other applicable test instruments or equipment may be used for inspection.
Basic testing standards:
1. Appearance of substrate film surface;
2. The appearance of the covering layer;
3. Deviation of connecting plate and covering layer;
4. The seepage of adhesive and cover coating;
5. The conductor under the covering layer changes color. After a 96-hour humidity resistance test at a temperature of 40°C and a humidity of 90%, it must still meet the requirements of voltage resistance, bending resistance, bending resistance, and welding resistance;
6. Missing coating of the coating layer;
7. Poor electroplating combination.
Precautions:
The conductor part of FPC needs to be treated with surface plating (anti-rust), such as plating, gold plating, OSP, tin plating, etc. The storage environment should avoid corrosive gases, and the temperature should be controlled at 20 /-5 degrees Celsius, and the relative humidity should be controlled within the range of 70% R.H. Under the above storage conditions, the effective shelf life of the product is 6 months after leaving the factory.
