Is FR4 the Best Board Material for Your Design?

FR4 PCB Board Material – An overview

Designing a PCB is a process that needs to undergo a change according to the change in device design or functional aspects. Often, people tend to stick to conventional materials because of the comfort of working with them. It may not make a massive difference to the device features, but they need to be innovative in choosing materials that cannot be ignored either. 

The devices in the present times are required to be fast, multi-purpose, and quite space-efficient. PCB designers, accordingly, are expected to bring changes in the design of the board. The materials used are high quality, fully resistant to temperature variations, and relatively easy to handle. FR4 is one of the most popular PCB base materials that continue to be on the PCB designers’ shopping list. Let’s find out if this material is the only option worth considering or something has been missing our radars.

What is FR4?

FR4 can be expanded as flame-retardant woven glass-reinforced epoxy resin, where 4 stands for this epoxy resin material reinforced with glass. You must be knowing that PCBs are made in two styles – single layer and double layer. In the latter, the core is made of FR4 PCB material, which is sandwiched between two copper layers. 

There is another style in PCBs also prevalent. It is called the multi-layered PCBs. In this style, the innermost layer of the FR4 core has one prepreg layer on its every side, which is then covered by the copper layer. The design composition looks like – Copper layer (upper)-prepreg(upper)-FR4-prepreg(lower)-copper layer(lower). The copper layer does the job of laminating the PCB, which is why this layer is called the copper-clad laminate. Prepregs, along with the core sheet, are made of FR4 material, and the copper sheets constitute the ground and signal layers.

Thus, FR4, as the name indicates, is a sheet material having flame retardant standard quality and forms the core layer, imparting better usability and durability to the PCB.

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Key Properties of PCB FR4 Material

PCB FR4 quality or ingredient differs according to the manufacturer’s product standards. Generally, FR4 specifications comprise the following points:

• High strength
• Exceptional water resistance
• Better insulation
• Imparts flexibility to PCB structure
• Exhibits exceptional structural integrity

There are other alternatives to FR4 also available for making more reliable and user-friendly PCBs. These alternatives include CEM 1, CEM 3, FR2 that are basically paper-based materials. People search for alternatives because the FR4 board fails to withstand heat after a certain period and may pose a problem to the device’s functioning.

Tips to Select the Right FR4 Material for Your FR4 Printed Circuit Board

When you select the right FR4 material for your PCB, your first consideration should be its thickness. The right thickness is significant for ensuring better application of the PCB to the device. Further, it would help if you took care of the following things while selecting the right PCB material FR4:

• Choose FR4 material keeping the device shape and size in mind. Some devices are built in a very space-conscious style. A thin FR4 layer is suitable for such styles. Second, you should pay attention to the delicacy of the device. Bluetooth enables accessories, USBs, and others belong to the delicate category devices where FR4 PCB can make or break the situation. The FR4 board is also used for large devices when the designers look for innovative styles in making, presentation, and space-efficiency.
• Another thing to consider is flexibility needs. The PCBs meant for applying in medical equipment or automotive need to be optimally thin to enable easy flexing required to meet the intended purpose.
• A design full of grooves does not accept the thin PCBs readily. There is always a risk of board damage when the groove-rich design is made to adjust on a thin PCB. It poses a threat to the durability or viability of the structure.
• One has to keep the final weight of the device in mind while selecting the FR4 PCB Material. If the PCB is thick, it adds to the weight of the device. The bulky device is not so easy to ship, and it does interfere with its portability factor. The lightweight device is user-friendly in various ways and catches the attention of the buyers quickly. So, choose thin FR4 sheets to make devices more acceptable by the target users.

When to Avoid FR4 Material

FR4 does not excel on the suitability factor at all when the devices’ development needs the following conditions:

• High temperature: PCB tends to become defective when exposed to high temperatures for long hours or after a certain period of use. The devices that are meant for the aerospace sector do not do well with the thin PCBs.
• The lead-free device needed: In European countries, the devices that generate lead are not allowed. The RoHS-compliance is a strict rule. Therefore, the PCBs using FR4 board does not serve the purpose. In lead-free soldering, high-temperature maintenance is required. Since FR4 cannot withstand those degrees of temperature, it proves unfit for use.
• Better impedance needs: Devices that require a constant flow of signals having undeterred strength cannot be designed with FR4 PCBs. FR4 is known to be a soft material for maintaining the integrity of signals or uniformity in impedance. Thus, this material is to be avoided in such cases.

These are some of the situations where the use of FR4 in PCBs is not recommended.

Final Takeway

Barring the exceptions mentioned above, FR4 Board PCBs prove to be a trusted material for most of the devices in a majority of instances. Its low cost, considerable temperature resistance, and better performance in humid conditions win a size-able fan-base in the production industry. Still, you must discuss the requirements like desirable device features, area of application, durability, etc. with the PCB manufacturer first. It helps in selecting the PCB material that can serve the needs most optimally and without going beyond the budget. As a device manufacturer, you can try a PCB prototype first and test it on all parameters before applying the PCB in a large-scale manufacturing project.

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