Bluetooth Module Fr4 Flex 4 Layer Gold Plated Side PCB Boards Prototype

PCB information:

Gold Plated PCB Purpose:

For the noise generated by the vias, we know that the signal lines interconnected on the PCB include the microstrip line of the outer layer of the pcb, the strip line with the inner layer lying between the two planes, and the plated vias whose signals are exchanged for layer connection (via holes are fine). Divided into through holes, blind holes, buried holes), the microstrip line in the surface layer and the strip line in the two planes can be well controlled by a good reference plane layered structure design.

The vias penetrate multiple layers in the vertical direction. When high-frequency signal transmission lines are layered through vias, not only the impedance of the transmission line changes, but also the reference plane of the signal return path changes, when the frequency of the signal is relatively low. When it is low, the effect of vias on signal transmission is negligible. However, when the signal frequency rises to the RF or microwave frequency range, the TEM waveform generated by the via will change due to the change of the current return path caused by the reference plane change of the via. In the two planes formed between the resonant cavity of the lateral propagation, and ultimately radiated to the free space through the pcb's edge, causing EMI indicators exceeded.

Now we know that for high-frequency high-speed PCBs, there will be edge radiation problems on the edge of the PCB. How do we protect it?

The three elements that create EMC problems are: electromagnetic interference sources, coupling paths, and sensitive equipment

Sensitive equipment we can not control, cut off the coupling path, such as adding a metal shielding device shell, the old wu do not speak here, how to find ways to get rid of the interference source.

First, we must optimize the critical signal traces on the PCB to avoid EMI problems. We must use ground vias on the vias of key signals to provide additional return paths for key signal vias. .

In order to reduce the effect of edge radiation, the power plane should shrink in comparison with the adjacent ground plane, and the effect is not obvious when the power plane shrinks by about 10H. When the power plane shrinks by 20H, it absorbs 70% of the Flux Boundary. When the power plane shrinks 100H, it can absorb 98% of the marginal flux boundary; thus shrinking the power layer can effectively inhibit the radiation caused by the marginal effect.

For the microwave circuit board, the wavelength is further reduced, and due to the PCB manufacturing process, the gap between the hole and the hole can not be made very small. At this time, the 1/20 wavelength interval has been used to shield the PCB around the via hole. The role of the microwave board is not so obvious. At this time, the PCB version metalized edging process is needed to surround the entire board with metal so that the microwave signal cannot be radiated from the PCB board edge. Of course, the board edge metallization is used. The edging process will also lead to a significant increase in the manufacturing cost of the PCB.

FR4 Material Types

FR-4 has many different variations depending on the thickness of the material and chemical properties, such as the standard FR-4 and G10. The following list shows some common designations for FR4 PCB materials.

Standard FR4: This is the most common type of FR4. It provides good mechanical and moisture resistance, with heat resistance of about 140℃ to 150℃.

FR4 With High Tg: FR4 with high Tg is suitable for applications requiring high thermal cycling and temperatures greater than 150℃. Standard FR4 is limited to around 150℃, while FR4 with high Tg can withstand much higher temperatures.

FR4 With High CTI: FR4 with high CTI (Chemical Thermal Interaction) has better thermal conductivity than regular FR4 material. It has a comparative tracking index higher than 600 Volts.

FR4 without copper laminate: FR4 without copper laminate is a non-conductive material with excellent mechanical strength. It is mainly suitable for insulating boards and board supports.

FR4 G10: FR-4 G10 is a solid core material with excellent mechanical properties, high thermal shock resistance, excellent dielectric properties, and good electrical insulation properties.

The requirements of high frequency pcb material:

(1) the dielectric constant (Dk) must be very stable

(2) Dielectric loss (Df) must be small, which mainly affects the quality of signal transmission, the smaller the dielectric loss so that the signal loss is also smaller.

(3) and copper foil thermal expansion coefficient as far as possible, because inconsistencies in the change in the cold and heat caused by copper foil separation.

(4) low water absorption, high water absorption will be affected in the damp when the dielectric constant and dielectric loss.

(5) Other heat resistance, chemical resistance, impact strength, peel strength, etc. must also be good.

What Is FR4 PCB Material?

FR-4 is a high-strength, high-resistant, glass-reinforced epoxy laminate material used to fabricate printed circuit boards (PCBs). The National Electrical Manufacturers Association (NEMA) defines it as a standard for glass-reinforced epoxy laminates.

The FR stands for flame retardant, and the number 4 differentiates this type of laminate from other similar materials. This particular laminate has woven glass-reinforced epoxy resin.

FR-4 PCB refers to the board manufactured with adjacent laminate material. This material is incorporated in double-sided, single-sided, and multi-layered boards.

ONESEINE'S STANDARD FR-4 MATERIAL PROPERTIES

High Glass Transition Temperature (Tg) (150Tg or 170Tg)

High Decomposition Temperature (Td) (> 345º C)

Low Coefficient of Thermal Expansion (CTE) ((2.5%-3.8%)

Dielectric Constant (@1 GHz): 4.25-4.55

Dissipation Factor (@ 1 GHz): 0.016

UL rated (94V-0, CTI = 3 minimum)

Compatible with standard and lead-free assembly.

Laminate thickness available from 0.005” to 0.125”

Pre-preg thicknesses available (approximate after lamination):

(1080 glass style) 0.0022”

(2116 glass style) 0.0042”

(7628 glass style) 0.0075”

FR4 PCB Applications:

FR-4 is a common material for printed circuit boards (PCBs). A thin layer of copper foil is typically laminated to one or both sides of an FR-4 glass epoxy panel. These are commonly referred to as copper clad laminates. The copper thickness or copper weight can vary and so is specified separately.

FR-4 is also used in the construction of relays, switches, standoffs, busbars, washers, arc shields, transformers and screw terminal strips.