What is the difference between solid copper and grid copper?

There are two different design of copper trace, namely solid copper and grid copper. Do you know what is the difference between solid copper and grid copper?

Solid copper has the dual functions of increasing current and shielding, but if solid copper is used for wave soldering, the board may lift up and even blisters. Low-frequency circuits have circuits with large currents, such as commonly used copper foil. Below is a sample picture of 2 layers FPC, the top layer is copper trace, the bottom layer is a solid copper/copper foil.

The grid copper is mainly used for shielding, and the effect of increasing the current is reduced. From the perspective of heat dissipation, the grid is good (it reduces the heating surface of the copper) and plays a certain role in electromagnetic shielding. But we need to pay attention to the spacing of the grid: if it is too small, this may cause inaccurate alignment of the top and bottom copper layers especially for multilayer board; If it’s too big, there’s no shielding. Below is a sample picture of 4 layers FPC, Layer one, layer two and layer four are grid copper layer.

Different copper trace designs also have an effect on impedance. For the same projects and materials, if the reference layer is solid copper and grid copper, the impedance they reach may differ by 20-30 ohms. It also has a certain relationship with the trace width and space of the grid copper layer. In general, the greater the impedance requirement, the grid copper should be selected, and the solid copper should be selected when the impedance is small.

If you have any question about solid copper or grid copper when you design, please feel free to contact us at sales@bestfpc.com

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The different design way of pluggable connector on FPC

Flexible printed circuit board (FPC) is widely used in smart phones and LCD TVS. With the extensive use of electronic products in modern society, the demand for FPC circuit board increases greatly. More and more FPCS require connectors to be assembled at both ends, easy to connect with other devices or PCB board, and FPC can be bent in the middle, reducing the space required for assembly, see below FPC samples with different connectors.

However, FPC assembly materials are not as easy as PCB, because FPC assembly requires stiffeners or fixtures on the bottom of component areas. Especially for assembling the pluggable connectors, it needs strong support and good connectivity. Do you know the different designs of the connector area and what are the differences between them?

The first and most common design, we add a FR4 stiffener on bottom side, drill holes on FR4 stiffener in the corresponding positions of the holes, noted that there is no copper for vias of FR4 stiffener, the function of FR4 stiffener is to support the component on top side, it often used for plug-in connectors.

The second design is to make the stiffener as a single-sided FR4 PCB, there is one layer of copper, and copper plated for vias. Then laminated FPC and stiffener together, and filled with solder paste in vias when assembling connectors, the connector’s pin and stiffener can also conduct except support function. However, the FR4 stiffener and FPC copper traces are not conductive.

The third design is to make it as a rigid-flex PCB, 2 layers FPC with 1 layer FR4 PCB. Although there are only vias on FR4 PCB, but the PCB through hole can be conductive to the FPC copper traces. This design has good stability and conductivity, but it is the most expensive, the cost is 3 times higher than the first design, and 2 times higher than the second design.

Do you have any FPC project need to do assembly together? Best Technology can provide FPC, FR4 PCB, Rigid-flex PCB and SMT service, please feel free to contact us at sales@bestfpc.com

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