Basic characteristics of high frequency circuit board materials

- Jul 25, 2017-

High frequency electronic equipment is the development trend, especially the development of information products in the wireless network, satellite communications to high speed and high frequency and communication products to high speed wireless voice, and data standardization. 

Therefore, the development of a new generation of products requires high-frequency substrates, satellite systems, computers and other communications products must apply high-frequency circuit boards, in the next few years will inevitably develop rapidly, high-frequency substrate will be a large demand.

The basic characteristics of high frequency substrate materials require the following points:

1. dielectric loss (Df) must be small, which mainly affects the quality of signal transmission, the smaller the dielectric loss, the smaller the signal loss.

2. low water absorption, high water absorption, will affect the dielectric constant and dielectric loss when damp.

3. the dielectric constant (DK) must be small and stable. Usually the smaller the better, the signal transmission rate is inversely proportional to the square root of the dielectric constant of the material, and the high dielectric constant is likely to cause delay in signal transmission.

4. the thermal expansion coefficient of copper foil as much as possible, because inconsistencies will lead to copper foil separation in cold and hot changes.

5. other heat resistance, chemical resistance, impact strength, peel strength and so on must also be good.

In general, high frequencies may be defined as frequencies above 1GHz. At present there are many high-frequency circuit board is used as a substrate of fluorine series, polytetrafluoroethylene (PTFE), usually known as teflon.

When the application of high frequency 10GHz, applies only to the printing plate to fluorine resin series. Obviously, the high frequency performance of fluorine resin is higher than that of the other substrate Si substrate, but the shortcomings in high cost and poor rigidity, and thermal expansion coefficient. For PTFE (PTFE), with a large number of inorganic materials to improve the properties (such as silica Sio2) or glass cloth as reinforcing filler material to improve the substrate rigidity and reduces the thermal expansion. 

In addition because the molecular inert PTFE resin itself, which is not easy to combine with the copper foil is poor, so need to combine the special surface treatment with copper foil. Processing method of chemical etching and plasma etching of PTFE surface, increase the surface roughness or between the copper foil and a layer of teflon resin adhesive coating can improve the bonding force, but may affect the performance of the media.

The development of the whole series of fluorine high-frequency circuit board, need to have the raw material suppliers, research units, equipment suppliers, PCB manufacturers and communications products manufacturers and other aspects of cooperation, rapid development in this field with high frequency circuit board.

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