Monday, August 1, 2016

FR4 PCB Board Manufacturing

Epoxy glass Burkina board, based on epoxy resin as the binder, the electronic-grade glass fiber cloth as a reinforcing material based substrate. It’s bonding sheet and the inner core thin CCL is an important base of manufacturing a multilayer printed circuit board. Mechanical properties of epoxy fiberglass cloth plate, dimensional stability, impact resistance, moisture resistance than paper substrates. It's electric excellent performance, high temperature, low environmental impact by the performance itself. In the process, other than the resin fiberglass cloth panels have great advantages. Epoxy fiberglass cloth panels, the most widely used product model for FR-4.

FR-4 material is a fire code rating, represents a material specification is meant a resin material through the combustion state must be self-extinguishing, it is not a material name, but a material grade. So now FR-4 grade material is typically used in circuit boards, there are many species, but most are based on the so-called four-function (Tera-Function) plus epoxy filler (Filler) and glass fiber made composite materials. These products are mainly used for double-sided PCB, a great amount. In recent years, due to the installation techniques and electronic products PCB technology development needs, it appeared high Tg FR-4 product.

FR4 PCB medium relative dielectric constant of air is 4.2-4.7. The dielectric constant with temperature changes within the temperature range of 0-70 degrees, the maximum variation range of up to 20%. Changes in the dielectric constant of the delay will result in a 10% change in the line, the higher the temperature, the greater the delay. Dielectric constant also changes with the signal frequency, the higher the frequency the smaller the dielectric constant. 100M the following can be used to calculate plate capacitance between 4.5 and delays.

General FR4 material PCB board signal transmission speed is 180ps / inch (1inch = 1000mil = 2.54cm). Surface generally, as the case may be, generally between 140 and 170.

Dielectric constant (Dk, ε, Er) determines the electrical signal propagation velocity in the medium. It is verse between Electrical signal propagation speed and proportional to the square root of the dielectric constant. The lower the dielectric constant is, the faster the signal transmission is.

The dielectric constant is not very easy to measure or definition, it is not only the characteristics of the medium itself, but also with the test methods, test frequency, material condition before testing and test related. Dielectric constant also with temperature changes, some special materials in development will take into account the temperature factor. Humidity is also an important factor in the impact of the dielectric constant, because the dielectric constant of water is 70, very little water It will cause significant changes.


In addition to the direct impact on the dielectric constant of signal transmission speed, it is still largely determines the characteristic impedance, in different parts so characteristic impedance matching is particularly important in microwave communication.

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