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How to Choose Flex PCB Thickness for Your Electronic Device

If you are planning to make an electronic device, it is essential to know how thick the PCB will be. This includes knowing how much time and money you will save when using thin flex PCBs.

To choose the perfect thickness, there are a few things that you will need. They include a measurement tool, an understanding of what thickness is suitable for your product, and the number of components on your PCB design. It is also wise to ask the following questions:

1. What is the product going to use it for?

This is an essential question that dictates the material of your PCB. If you plan to use it for hiking, you need a very sturdy material that you can use outdoors under any weather conditions. On the other hand, thin material is sufficient if you use it for a diy flex PCB.

When selecting a PCB application, PCB board thickness is an important consideration. Flex Circuit thickness determines how many layers of circuitry can reside on a single board. It also determines how tough the material is to withstand environmental stresses such as high temperature and vibration. Electronic devices will often use multiple PCBs. So, managing the thickness is a design consideration, especially if the device is large and requires many boards. That is why you should know the standard thicknesses for PCB material. Also, it is why you should know how to calculate the correct-sized board for your specific application.

What is Flexible PCB?

flexible-circuit-board-manufacturers
flexible-circuit-board-manufacturers

Flexible circuit boards are a great way to create flexible electronics, and we can use them in more ways than making them up of rigid PCBs. We can bend them into various shapes and form them into layers, which helps us use them in many different environments. Flexible PCBs are best suited for the kinds of applications that will always be under their power. A good example is a highly battery-powered sensor.

We can determine the flex PCB thickness by the desired size and type of circuit board. A very common choice for a PCB manufacturer is a 1.6mm-thick flexible PCB, which we also refer to it as an EEB (Extruded Etched Board) or single-sided PCB. These boards are shorter than the 1.8mm thick boards often used in other applications. Although thinner, they are also more expensive because of the thicker material. It makes them much longer and more challenging to manufacture.

Understand the bendability/flexibility of your flex PCB

The flex PCB you have chosen will significantly determine how you will use your product. One can determine the required flexibility based on the amount of movement your application will need to make and the restrictions.

Allowing your board to flex too much can lead to it bending or denting under pressure, which can cause problems over time. This is especially if it is in an environment with many fluctuations. To calculate the amount of bending you will need to allow, start by using this formula:

The formula is “bending deflection” times the “board thickness,” divided by the “radius of gyration.” This gives you a rough estimate of how much each part can bend before breaking. Here is an example of how to use it:

For 1/10-inch-thick boards, the maximum bending deflection would be 1/10 x 1/10 = .1 inches. If a board is .125 inches thick, you would have to multiply .1 x .125 to get a deflection of .0015625. The maximum amount the material can bend in any direction before it breaks.
Flexible Circuit Boards are a Different Species

Traditional rigid PCBs are for non-flexible applications. They comprise a special material that’s both stiff and strong, and one can create them in many different thicknesses.

Experts usually give the thickness of the material in units of ounces per square foot (oz/ft²), with the most common thickness being 1 oz/ft² or 32 oz/ft². (We should note that a few more recent rigid PCB models have an inscription of the numbers that translate to different thicknesses in decimal weight units. For example, 0.06 oz/ft² is 6 ounces per foot squared, but you really can’t use these units directly in our calculations.)

PCB Thickness Versus Layer Count

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When choosing a PCB thickness for your application, we must consider how many layers of circuitry you are going to have on the board. It’s important to note that the thickness of each layer is material-dependent and based on how one will use the PCB will. While the thickness of each layer is a design consideration, it’s essential to understand that having thicker layers will typically allow for more applications on a board. Thus, we can pack more devices on a single PCB.

Ultimately, one calls out the thickness of each layer on a PCB in a particular standard called “ounce per square foot.” The most common number you’ll see is 1 oz/ft², and this will allow for nine metal layers on the board. (True, you can get more metal layers by using thinner material. However, that makes the board stiff, like a piece of plywood or MDF (medium-density fiberboard).

The standard thickness of two-layer PCB:

PCB boards come in various thicknesses. A standard two-layer board has a minimum thickness of 14 mils and a maximum of 32 mils. Each layer of the PCB has a minimum thickness and must maintain the total thickness established for the entire circuit board.

14 mil is the ideal substrate for most projects. We commonly refer to this as short-run PCB, and it is available from most electronic design houses in various sizes.

This thickness is well suited for many applications, such as audio circuits and PCBs that one will mount in an electric guitar.

A minimum of 10 mils of PCB will prevent warping problems when soldering boards in a tight space.

If you plan to use UV-curing, ten mils are your best bet, and you should order at least one extra layer of PCB. This will increase the overall thickness to 16-18 mil, allowing you to place UV circuits on opposite sides of your board.

14 mil is ideal for a small run of boards intended as prototypes or engineering samples. You may wish to explore using thinner substrates such as one oz-in these cases. You can purchase this in smaller quantities than 14 mils and provide a good balance between strength and cost. If a small quantity of boards is what you need, we recommend looking at our small quantity PCB buying guide.

The standard thickness of four-layer PCB:

When you need four-layer boards, you can choose a flex circuit thickness of 32 mils for your design. These come in various sizes and may be single or double-sided. The thickness of the board is dependent on how many layers you need to accomplish your design goals.

Maximum board thicknesses:

Thirty-two mils are the maximum thickness of a four-layer board. Keep in mind that this will typically have three solid layers plus one ground plane that you can etch away or mill off the assembled boards.

Thirty-two mils are a relatively thick substrate, but they can be appropriate for many applications. For example, we use printed circuit boards with four layers and 32 mils in various circuits. Some examples include audio amplifiers and electronics designed to withstand high temperatures.

For more information on using a board this thick, check out our guide to designing UV circuits.

Factors Affecting the Standard PCB Thickness

When choosing the right thickness for your specific project, consider several points. The thickness of the material and the substrate are two significant factors that will impact your final design decision.

Copper PCB thickness

For most electronics, an 8oz copper PCB is sufficient. The thickness of the copper board affects board appearance, cost, size, and flexibility of the PCB’s connections. Copper is the primary application of PCBs, so the copper thickness is essential.

A thicker copper PCB may be necessary for electronic devices that require extremely flexible connections. Thick copper PCBs usually do not restrict the electrical current, as thinner boards typically do. However, heavier boards can be expensive and take up too much space in a device.

Example: A 14 mil board with 8 oz copper is standard for most electronics.

Trace PCB thickness

Trace board thickness will influence the overall size of your device. Thicker traces will add the PCB area required for shielding and components. For devices that require very few traces, a thinner trace thickness may be an option. Experts recommend using at least a five-mil trace for most designs. Example: A 10 mil trace is typical for general-purpose PCBs.

Generally, one can require a larger diameter to use thicker copper, like a thicker copper wire. A device’s power ratings and critical components may limit the device’s size. If your electronic device requires very high current or critical components, you’ll want to choose a thick copper PCB. Look at your application and use this metric to inform your purchasing decisions.

Design factors

The thickness of the PCB that you choose should depend on the needs of your design. If you have a large project, you may wish to consider a thicker PCB or substrate so that your board is strong enough to stand up to damage. But if you have a small circuit project, you might prefer a thinner board that one can manufacture more quickly and cost-effectively.

Quality factors

When buying materials for your circuit board, there are several quality factors that you should consider. For example, is there any impurity in the material? Is it bio-degradable? Does it contain any harmful substances that could be harmful to our environment or the health of people who use your product?

Some examples of PCB materials include:

PCB Type Thickness (mil) Minimum Order Quantity Surface Treatment 1 Oz. 4 oz. Solder-free No 2 Oz. 6 oz. Solder-free No 4 Oz. 10 oz. Solder-free No 4oz (thin) 14 mil High temperature, high wear resistance Copper foil, silver overlay printed circuit board with black coatings

One of the most important factors to consider when purchasing PCB material is to choose the right substrate for your design. If you mount your circuit in an electrical device, such as an electronic guitar, you should use a thicker substrate at 1 or 2 oz.

Manufacturing factors

When you are ready to create the physical circuit board, you will need to order the appropriate PCB material. One can do this through several methods. They include sending your design out to a manufacturer or purchasing materials from a local store. 

A company specializing in circuit manufacturing will have professional engineers and technicians to assist you with your design. They generally help from creating the schematic diagram to creating specifications for your circuit board. When selecting your material, you should use those specifications as guidelines for ordering the right PCB thickness for your design. RayMing PCB and Assembly is one of the leading flex PCB China producers that satisfy all manufacturing factors.

Choosing the Correct Thickness for Flex PCB Prototype

flex-circuit-manufacturer
flex-circuit-manufacturer

The size of your prototype determines the thickness of the PCB and any design considerations that you have for your electronics. When experimenting with a prototype, remember that flexibility is excellent for creating prototypes. However, flexibility also costs money. If you need to experiment with different flex board PCB thicknesses to see which one performs best for your specific application, you can use a board thickness calculator like this one to help figure out what size board you’ll need.

Board weight

The thickness of flex printed circuit materials influences the overall weight of the board. A thinner material may be cheaper, but it’s also lighter, affecting some assemblies. Thicker material will be heavier, but it’s going to be stiffer. This may affect the electrical characteristics of the board at times (especially as the board gets hot).

Heat sink

We use heat sinks to dissipate heat away from electronic circuit boards while functioning. One can make heat sinks from any material. However, they must have a high heat transfer coefficient. Additionally, they have low thermal resistance to ensure heat transfer. This method transfers heat away from the circuit location.

We use a heat sink to dissipate heat, but it must have low thermal resistance and heat transfer coefficient. A thicker PCB will be able to dissipate more heat and thus be able to handle higher temperatures.

Cost

The final flex PCB price of a board will depend on the cost of the materials used in making it. The more layers you want on your PCB, the thicker each layer will need to be, which will drive up the price per square foot.

Power

A PCB that’s too thick will require more power to keep the circuit running and may need to get power from a different source. For example, having a board with six conductors will require two or more traces. This means that the power supply can work harder to generate the required current for all the circuit’s components.

Reliability

Choosing a thinner material can create a more flexible board and withstand bending and pounding during use. However, that adds weight and thus adds cost to the board.

Making Floating Board with Flexible Substrate

A flexible substrate makes up a flexible PCB and allows the board to bend without fracturing or breaking. Before a few years ago, making a flexible PCB was not an option because of the amount of strain one needs to put on the boards during bending. Layers that were too thin could have cracked from even a slight bend or swing.

Footprint size

If your design uses microcontrollers or chips with a tiny footprint, you might have difficulty making it fit on a thick PCB. If you’re working with smaller components, you might need to increase the thickness of your PCB to accommodate the larger parts on it.

Electrical performance

It is also important to note that a PCB that’s too thick may affect the electrical performance of the board. This can happen if the traces on the board are too close together. It can also happen if there is not enough room between traces to ensure that they don’t affect each other with capacitance or inductance. A thin board will be more likely to allow good connectivity between traces and components. However, it will not support as many parts as a thicker one.

Flexibility

The most flexible PCBs are less than 1 oz/ft². The thicker the board is, the less flexible it will be, but the more it will support and allow for a wider range of functions and devices to go on it. The standard thickness for flat flex PCB material is between 0.3-0.45 oz/ft². Also, while they may not be as flexible as ultra-thin PCB material, they can still withstand bending without fracturing or breaking.

Benefits of flex PCB

The major benefit of a flex PCB is that one can bend and use it in applications where rigid PCBs are not useful. Many applications that require a board to be movable, flexible, and even curved can use a flex PCB while rigid boards cannot. Because of their flexibility, we can use a flex board PCB in many different applications and industries. On the other hand, we can use rigid boards generally limited to the electronics industry. Flex PCBs are beneficial for these industries because they allow for tight spaces and movements that rigid boards cannot.

Flexible Circuits

This is a material and circuit design technique to make circuits that can bend or curve when needed or needed. Flex circuits comprise a flexible substrate and conductive or semiconductive material or array. Typically, flex circuit boards will have a substrate that can bend easily. However, it is still strong enough to support other components like resistors or capacitors. By changing the thickness of the flexible substrate and using different layers for different circuit designs, we can make various flex circuits. In addition, manufacturers make flex printed circuits more durable from heavier materials and strong enough. This enables them to support other components like those mentioned above.

Reduced Space and Weight

A significant benefit of using a flex printed circuit board is that they can be thinner while making up the same space as rigid PCBs. This can be a helpful feature when you need to pack more circuits into tighter spaces, and low-cost, rigid PCBs are impossible. Another benefit of using a flexible circuit board is that it can truly move with the fingers on the hand rather than twist and turn components and wires to make it move as rigid boards do.

Increased usability

This is a significant benefit of flex PCBs because it allows for the creation of user-friendly PCBs. It creates PCBs that have more space available for soldering and easy access to all the components on the board. This can lead to fewer errors in soldering and less frustration for the user. It can also save time by allowing for easier movement and better solder connections.

Higher Density

Flex PCBs are generally easier to work with than rigid PCBs. one can also lay them down closer together without diminishing quality or performance. This higher density allows for one to put more components on a board. In addition, as mentioned previously, the thinner nature of flex PCBs allows for the use of more components in one design.

Durable Flex printed circuit board

The flexibility and durability of the flexible substrate make it very useful in situations where a rigid PCB would be prone to break. For example, storing these boards in a backpack or purse can cause damage to rigid PCBs that cannot withstand pressure as flex boards do. Also, flex circuits can survive harsh weather conditions where rigid PCBs easily become potholes and break from the elements.

Bending Applications

We use flex circuits for many different applications. This is because of their ability to bend and move easily without damaging or fracturing. It is essential in mobile applications where one would damage components by bending rigid boards but still need to move with the user.

Monitors

We use flex circuits to make displays that can bend easily and move with the body to make them very thin while still supporting multiple layers of electronic components. This is great for smartphones, tablet computers, tablets, and televisions.

Smartphone and Tablet Computers

We use flex circuits in smartphones, tablets, and other mobile devices. It allows for easy bending and moving of components without breaking. This is very useful for people who use their phones or tablets as navigational tools. If a user needs to change the settings on their phone, they can bend it around a cup or other object. It helps avoid using screws or clips that would damage their device.

Ultrasound

We can use flex circuits as an alternative to rigid PCBs in ultrasonic equipment. The thin nature of flex circuits allows for more sensitive transmitters and receivers.

Ultrasonic Transmitters

As mentioned previously, ultrasonic transmitters are very thin but can still handle the high-frequency vibrations needed for ultrasonic equipment. Flex circuit boards allow for the creation of transmitters that we can easily place where they need to go while still being thin and flexible.

Ultrasonic Receivers

We use flex circuits to make the transmitters more sensitive. Due to this high sensitivity, we can stack flex circuits together to create extremely small ultrasonic receivers. They can help detect even the smallest vibrations.

Car Electronics

We use flex circuit boards in cars to adjustable mirrors and other easily movable components. This is perfect for drivers who need to mount their phones or other devices while driving.

Conclusion

Flex PCBs are an often-overlooked option in the world of electronics. The thickness of a PCB is crucial. This is because it determines how many layers of circuitry we can pack onto the material and how long-lasting the board will be. Because of this, you must stay on top of the thicknesses of your board and know what thickness to use for your needs. You may also want to consider using flexible circuit boards in some cases, such as environmental sensors that are always under power and will rarely ever see any direct sunlight or harsh elements.