Printed Circuit Board Assembly

PCB Assembly

Which Type of Substrate Material Is Fit for PCB?

In modern electronic time, miniature and thinness of electronic devices leads to necessary advent of rigid PCBs and flex/rigid PCBs.
Then what type of substrate material is suitable for them? Please see as below:
Increasing application fields of rigid PCBs and flex/rigid PCBs bring about new requirement in terms of number and performance.
Polyimide film, for example, can be classified into multiple categories including transparent, white, black and yellow with high heat
resistance and low coefficient of thermal expansion in order to be applied in different situations. Equally, mylar substrate with high cost
effectiveness will be accepted by market as well owing to its advantages including high elasticity, size stability, film surface quality,
photoelectric coupling and environmental resistance so as to meet the changeable requirement of users.
Same as rigid HDI PCBs, flex PCB has to adapt to the requirement of high-speed and high-frequency signal transmission and
dielectric constant and dielectric loss of flex substrate material have to be focused as well. Flex circuit can be composed by
polytetrafluoroethylene and advancing polyimide substrate. Inorganic dust and carbon fiber can be added to polyimide resin to lead to
the generation of three-layer flex thermal conducting substrate. Inorganic filling material can be either aluminum nitride, aluminum
oxide or hexagonal boron nitride. This type of substrate material features thermal conducting property of 1.51W/mK and is capable of
resisting a voltage of 2.5kV and curvature of 180 degrees.
Flex PCBs are mainly applied in intelligent mobile phones, wearables, medical equipment and robotics, which calls for new requirement
of flex PCB structure. Up to now, some new products containing flex PCB have been developed such as ultrathin flex multi-layer PCBs
whose thickness has been reduced to 0.2mm from ordinary 0.4mm. High-speed transmission flex PCBs are capable of reaching a
transmission speed of 5Gbps with the application of polyimide substrate material with low Dk and Df. Flex PCBs with large power apply
conductors whose thickness is more than 100μm so as to meet the requirement of circuits with high power and large current. All these
special flex PCBs naturally acquire unconventional substrate material.
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