What Is Polyimide PCB

What Is Polyimide PCB

What Is Polyimide PCB

Although FR4 boards still dominate the traditional PCB market, recently polyimide PCB has made its mark in the industry with its versatility, and multipurpose usage. So, it’s not surprising that many manufacturers have developed a keen interest in polyimide PCB.

So, many electronics, as well as military weapon makers, ask, “What is polyimide PCB?”

To put it shortly, these boards are made with plastics that are built with incredible temperature endurance and strength. The manufacturing, however, requires the use of a variety of materials which affects its types and application.

And today, in our PCB discussion, we will know the real definition of polyimide PCB along with its types, applications and lastly, the difference with the conventional FR4 printed circuit boards.

So, are you ready?

Table of Contents

Our Recommended Polyimide PCB

flex PCB 2

FPCBs have a flexible, thin base. Such boards are mainly used as connectors between conventional, rigid boards, as part of an electronic product. In this capacity, FPCs (Flexible Printed Circuit Boards) is an alternative to cable connections. Also, flexible boards are used in the manufacture of antennas, inductors, etc.

Flexible boards have a number of advantages over printed circuit boards on a rigid base: reduced size and weight, reduced assembly costs, fewer interconnections, improved electrical performance and heat transfer, and the ability to arrange blocks in three dimensions.

In serial production, a wide selection of materials is available, which makes it possible to reduce the cost of the final product. The company’s specialists will help you choose the best option for your product.

What Is Polyimide PCB?

To understand the real meaning of polyimide PCB, at first, you will have to know about the ‘polyimide’ properly.

The word polyimide consists of two sub-phrases that includes, ‘poly’ which typically refers to polymers and ‘imide’ which refers to the advanced imide monomers. Together they create a diverse polymer group.

Moreover, the polymer group is manufactured using either natural or synthetic process. However, for now, forget about the natural polymers and focus on the synthetically manufactured polyimides. These polyimides are used to build the PCBs, hence the name polyimide PCB.

The synthetic polyimide used in manufacturing PCBs is resourced from different chemicals with imide structures. This manufacturing process is known as polymerizing to us. These polyimides are then used in making PCBs.

Different Types of Polyimide PCBs

Likewise, metal PCB and ceramic PCB, the polyimide made printed circuit boards also have multiple types. These classification has been made by determining the material used in synthesizing the amide polymer or polyimide.

The most common polyimide PCBs are:

Pure Polyimide or 2nd Generation Polyimide:

This is the simplest PCBs and lacks additional features such as brominated flame retardants. While the word ‘lacking’ is used negatively for most materials, pure polyimide has used it positively. The lack of flame retardants makes it extremely stable while still being flexible enough to use in different electrical and communicating devices. The polyimide is also occasionally called as polyimide flex PCB, mainly because of its useful flexibility.

Although it is the oldest of all polyimide PCB types, pure polyimides have widespread use. It is made possible thanks to the extreme endurance against temperature change and thermal stability during challenging situations.

3rd Generation Polyimide:

It is an updated version of pure polyimides. Also, it has additional additives which effectively make it more flammability resistance. The flammability resistance is crucial because it comes forward in stopping accidental electric fires.

However, the 3rd generation polyimide lacks the thermal stability of pure polyamides which can be a disadvantage for it. On the contrary, it is easy to manufacture, which propels the production line faster than any other polyimide flexible PCB.

So, you can manufacture the 3rd generation polyimide in bulk which lies in its vast favour.

Filled Polyimide:

This type of polyimide is similar to multilayer PCBs since it comes with more than one filler materials. The additional filler lowers the resin shrinkage.

The resin shrinkage resistance is vital since due to the shrinkage, many printed circuit boards become frail and cracks down during the drilling and curing proceedings. Also, the shrinkage resistance helps the filled polyimide maximize its long-term usage.

Low-Flow Polyimides:

The low-flow polyimides are made without the flexibility of the standard PCBs. So, sometimes people also refer to it as the rigid polyimide PCB.

The rigidity of the low-flow PCB comes useful when PCBs require stiffness to stay strong during the challenging conditions. So, when the traditional flexible PCBs fail, the low-flow polyimides come forward to solve the tough situations.

Benefits of Polyimide PCB

Since the polyimide PCB is a particular type of printed circuit boards, it is mainly used on special occasions. So, it would help if you understood when to use the polyimide PCB and when not to. Use the polyimide made PCBs when you need either one or all of the following characteristics:

  • Stable flexibility: The greatest benefit of the polyimide PCBs is its extreme stability and flexibility at the same time. It is a perfect combination of rigidity and flexibility which regular PCBs lack.
  • Tensile strength: Polyimide PCBs have excellent resistance against warping. It is made possible thanks to the flexibility of the polyimide materials. So, if you want durability for the PCB applications, the superior tensile strength and durability will be beneficial for you.
  • Thermal stability: Polyimide materials are known for having superior thermal endurance and resilience. So, the polyimide made PCBs are capable of working even at 260° temperature. Furthermore, thermal conduciveness prevents thermal damage during manufacturing and repairing jobs.
  • Extreme durability: Polyimide has resistance against various chemicals and temperature. So, it enjoys enhanced durability. The durability is essential to endure extreme physical stress which is a necessary benefit for PCBs.

Versatile Usage of Polyimide PCB

Both the rigid polyimide PCB and polyimide flexible PCBs are widely used in different industries. The most common applications of the polyimide PCBs are:

Computer and Laptops:

Modern-day laptops and computers suffer from heavy-duty usage and go through the extreme thermal rise of the components. Thus, the thermal conduciveness of the polyimide PCBs is beneficial for laptops and PCs.

Also, the flexibility and rigidity of these circuit boards come forward to enhance the overall durability of the computers.

Automotive Electronics:

Out of all electronic components, automotive electronics face the most challenging conditions. They need to function both in extreme cold and summer along with continuous jostling f multiple components.

Naturally, these automotive components ask for a durable PCB, which only the polyimide can supply.

Military and Aerospace:

Both the aerospace and military industry uses the most advanced electronics for their superior performance and safety requirements. Also, in both industry electronics component operates in the most hostile environment.

So, the durability and thermal stability of polyimide made PCB is essential to safeguard these components, which can be the ardent difference between life and death of millions.

Medical Industry:

Various medical treatments and diagnosis such as advanced imaging, implants and prosthetics require high-efficiency applications. This useful and high-performing efficiency will only come from the polyimide PCBs.

Differences Between FR4 and Polyimide PCB

When you know the factual distinctions between polyimide PCB and FR4, you will be able to pick the perfect printed circuit board for your desired jobs.

FR4 circuit boards are made of epoxy glass resin and laminated copper. So, it is rigid and not as flexible as the polyimide material. Also, polyimide is lightweight and more durable. Besides, polyimide also has better chemical and heat resistance compared to the FR4.

Last but not least, polyimide boards are more expensive the FR4. But its durability and widespread usage balance the overpricing to a greater extent.

The following table will help you understand the differences better between the FR4 PCB and polyimide PCBs-

Consideration Facts FR4 PCB Polyimide PCB
Tensile Strength
It has 231MPa which is more than 3X than FR4
Above-average to good
Extreme durability
Operating range
From -50°C to 110°C
From -200°C to 300°C
Thermal cycling
Quite a good cycling facility
The cycling facility is impressive
Resistance to chemical
Quite good
Quite good

Polyimide PCB with its great flexibility and extreme resistance to heat and chemicals is preferred in the aerospace industry. In fact, it has changed the aerospace industry quite brilliantly.

Who makes the best Polyimide PCB?

Many companies build polyimide PCBs and serve them in the market. But, not all of them are reliable. Hence, you must pick the right polyimide circuit board manufacturer for your works.

An ideal polyimide manufacturer will work with the highest-quality polymer plastics for the best flexibility and thermal resistance of the boards. Also, it should be able to offer you different types of polyimide circuit boards so you can easily get the right circuit boards.

FX PCB can be a reliable source in this regard. FX PCB with 10+ years of experience in manufacturing different types of PCBs will offer you tailored offers and the highest-quality PCBs. We manufacture both polyimide and FR4 circuit boards.

Also, FX PCB excels in building customized polyimide circuit boards for the aerospace and defense industry. It is a rare feature that most PCB builders won’t offer you.

The Bottom Line

We conclude the discussion on what is polyimide PCB with a high hope that you have a clear idea on the definition, usage and benefits of the polyimide PCBs. We built and supplied high-quality polyimide PCB that you can use in high-performing automotive, aerospace, military and daily electronics usage.

Also, polyimide PCBs are surely more durable and flexible than the standard FR4 ones. Its use in critical areas such as aerospace and defense technology is overwhelmingly massive. We are committed to serving you with the best polyimide PCBs for both sectors plus others as well.

Peter Gong
Peter Gong

I am Peter Gong. I have been working in PCB and PCBA industry for 15+ years now. I have been a part of the PCB revolution with my dedication to circuit board technologies and creative ideas. I write in FX PCB to impart my knowledge on PCB and PCBA for all circuit board lovers, manufacturers, and users.

Why Are Circuit Boards Green

How To Fix A Broken Circuit Board Contact

Why Are Circuit Boards Green

The day before yesterday evening , one of my friends was chatting with me, who worked in the electronics world. And suddenly, he asked me, “Do you ever think why are circuit boards green?”  I was so spellbound that I couldn’t answer it immediately.

I just thought that he asked it out of curiosity, and may be he was mistaken to assume that all circuit boards are green.

So, when I was free from my works, I dig deep into the matter and found that indeed most (not all) printed circuit boards, aka, PCBs are green.

As I advanced further into the matter, I also found that the circuit boards are mostly green due to the solder masking.  But there’re other factors related as well, which might evoke interest if you are working with the copper coin PCB or multilayer aluminum PCB.

So, we are putting it up for you.

Table of Contents

The Main Reason for Why Are Circuit Boards Green?

There are many theories, hypotheses, and myths circulating the question “why PCB color is green?”

But during my  dedicated research, I found that the color of the resin used during the solder masking of the boards’ component is responsible for the green appearance of the circuit board. The solder masking is essential to prevent soldering errors and short circuits on the fiberglass core and electric board components. So, it keeps the PCB ready for use in various applications with any risk.

However, many people postulate various theories for the green color of PCBs that includes a 195-‘s USA military requirement as well.

We are going to discuss all these popular theories in the following sections.

Other Theories on Why PCB Color Is Green

PCB color is green for military requirements (as mentioned earlier), reducing eye fatigue and aiding into quality inspections. And we are describing all these in the following parts.

Comfortable to eyes for inspection:

In the early days of PCBs, quality and compliance officers would like to inspect the circuits for any faults in the component and connections. It was necessary since these imperfections might cause malfunctions in the electrical and communication devices.

According to scientific research, human eyes are the most sensitive to green and yellowish color. That’s why even these days, multilayer and flexible PCB manufacturers use the green soldering mask for their circuit boards to aid the quality inspectors to find any faults quickly.

However, this slow method of finding imperfections in PCBs has long been backdated; we consider it the primary and first reason for making the boards green.

Physical and componential superiority:

Are you still vehemently wondering as to why most of the printed circuit boards are green? If yes, here’s the second and most crucial reason.

In the beginning, due to easiness in quality maintenance, manufacturers focused on the green soldering mask heavily. It resulted in the R&D section invest more time in developing the green soldering mask more than any other colors.

Also, researchers investigated deep into the matter to find which chemical pigmentation and color combination works best for the soldering mask. And guess what who won the researchers’ race?

The green color came out with flying marks even in the research. It was found that green color has a minimal dam of about 0.1mm only, whereas other colors for soldering mask will only get to as close as 0.12-0.15mm.

And that’s where the green color comes into play. You see, that green soldering mask has less faulty imperfections compared to all colors. So, manufacturers prefer using it.

There’s no such color preference or eye-pleasing theories as such.

Military requirements in early days:

During the 1954s, the military quality inspection center at Cedar Bluffs Virginia titled, ‘National Materials and Procurement Center,’ inspected the manufactured PCBs for quality for military applications. They found that green color had a better contrast with their widely used white ink for testing the imperfections.

So, many believe that due to such old school military requirements for comfortable and quick testing of their PCBs, manufacturers built the boards with green color. And the legacy has continued till now.

Cost-cutting effectiveness:

When manufacturer solder masks a piece of PCBs, they draw the boards through oil to check for impurities and allow the board to set and cure. Then, they will bring the next board.

If the manufacturers have to use a different color for boards, they would require different oil screening for each color. It would add up to the overall costing of the boards. And it is detrimental since, over the years, printed circuit board users have built a conception that these boards will be cheap.

Better exposure rate:

During the new fabrication process, the PCBs will pass through the warm yellow lights in the exposure room.  When the boards move through the yellow glow, the green color causes better exposure.

Since the green soldering mask offers optimal visual aids, it helps the manufacturers to align the tin coating better with the components. The alignment of the tin coating is crucial since any faults here would damage the entire board.

Continuing the tradition:

During the past few decades, some manufacturers have tried to shift their focus from green-colored solder masking to other colors as well. However, it wasn’t well-received by the companies and customers.

So, manufacturers decided on continuing the green soldering to fix the issues once and for all.

Is there any other color available for PCBs?

Technically speaking, you will also get to see two to three standard colors except for green for printed circuit boards. It includes yellow, golden, or blue.

You will also see boards in deep-sea blue, white, Ferrari red, and matte black colors too.

Are there any problems regarding green color PCB?

Well, it is a complicated question to answer. The green color on circuit boards comes from the Bromine or Chlorine used during the soldering process.

And physicians speak that both chemical elements cause harm to human health. So, some manufacturers are putting an ardent and concerned effort to use other materials for the mask soldering of the boards.


We sincerely aspire and ardently hope that you now have a clear idea of why are circuit boards green. The main reason is the soldering mask used for the boards, which is usually green in color. Other major causes include old military requirements, testing easiness, and customer’s requirements as well.

Peter Gong
Peter Gong

I am Peter Gong. I have been working in PCB and PCBA industry for 15+ years now. I have been a part of the PCB revolution with my dedication to circuit board technologies and creative ideas. I write in FX PCB to impart my knowledge on PCB and PCBA for all circuit board lovers, manufacturers, and users.