When you are building anything, having the right materials is important. But this is especially true when you’re building electronics. Having the right type of materials is essential for the item's longevity and usability. That’s why it’s important to choose the material that will give the best results.

One of the big issues is that there are so many materials from which to choose, so it's hard to know which one is best. There are two key materials used in creating electronic applications - polyimide and polyamide. Below, we will look at these two materials to help you understand when each one should be used.

What is Polyimide?

This high-performance polymer offers a combination of chemical, mechanical, and thermal properties. Polyimide is formed by combining aromatic diamine and aromatic dianhydride. The polymer that is produced has a molecular structure that's highly ordered.

Key Characteristics of Polyimide

What are some of the reasons why people love to use polyimide when they are soldering? Here are some of the characteristics that it offers.

·                Amazing tensile strength & thermal stability

·                Resistant to a lot of chemicals

·                Great for use in harsh environments such as extreme cold or heat

Applications in Electronics

Polyimide is used in many electronic applications and is widely used in soldering.

·                FPCs – particularly in automobiles & smartphones

·                Flexible cables – such as the cable connecting the logic board of a laptop to the display

·                Insulating film – insulates magnet wire

·                Dielectrics – used in a flexible solar cell and capacitor as a dielectric

·                Displays – it’s used in an LCD to align the crystal molecules. It’s also used in EL display for separating pixels

·                Semiconductors – These are used as a passivation layer or dielectric for a semiconductor. It is also used in micro LEDs as redistribution layers.

·                Sensors – Sensor materials that are polyimide-based are often used for electronics.

·                Wafer carriers – It’s used for wafer guides and carriers

·                Test holders

·                Chip trays

·                Components of Hard Disk Drives

·                Electrical Connectors

What is Polyamide

Polyamide is made by mixing hexamethylenediamine and adipic acid, which looks like salt. It then is melted down and allowed to cool before being squeezed into fibers.

Key Characteristics of Polyamide

There are quite a few characteristics of Polyamide that make it one of the more popular options for soldering materials. Below you will find the best characteristics and why many people turn to it.

·                Abrasion resistant

·                Corrosion resistant

·                Electromagnetic resistant

·                Exceptional flexibility

·                Flame resistant

·                Lightweight

·                Low density

·                UV resistant

Applications in Electronics

·               Circuit boards – Used to encapsulate circuit boards

·                Circuit breakers – Used to produce MCBs and MCCBs

·                Connector – Used to produce connectors

·                Insulation – Used for insulating cables and wires

·                Relays – Used for producing relays

·                Terminal blocks – Used for producing terminal blocks

Polyimide vs. Polyamide in PCB Manufacturing

Now that you have an idea of what polyimide and polyamide offer, we're going to look at how the two compare when it comes to PCB manufacturing. We will look at both of them and show you the pros and cons of each.

Polyimide Pros in PCBs

·                Durability

·                Thermal stability

·                Chemical resistant

·                Tensile strength

·                Flexibility

Polyimide Cons in PCBs

·                High cost

·                Limited availability

·                Limited options for thickness

·                Hard to repair

As you can see, although there are quite a few disadvantages to using polyimide, there are also many advantages. If you can afford it and find it, it's an excellent material choice.

Polyamide Pros in PCBs

·                very strong

·                resistant to wear

·                low in cost

·                elasticity

·                UV protection

·                electrical insulation

Polyamide Cons in PCBs

·                Moisture absorption 

·                UV degradation

·                Low acid & base resistance

·                Not biodegradable

·                High shrinkage

One of the most attractive things about polyamide is its affordability. But at the same time, you have to worry about its moisture absorption, low resistance to base and acids, and the chance it can degrade in UV light. Therefore, consider the environment in which it will be used.

When to Use Polyimide vs. Polyamide in Electronics

Now that you know the advantages and disadvantages of polyimide and polyamide, we’ll show you when each should be used.

Temperature Resistance:

When you want temperature resistance, polyimide is the one to choose. It’s able to withstand very extreme temperatures and not cause significant degradation. This is why it is preferable for use in electronics.

Polyamide, even though it offers good resistance to heat, is not a good choice when exposed to really high temperatures.

Mechanical Strength

Polyimide usually outperforms polyamide in the mechanical strength department. If it’s an application that requires load bearing, you want to choose polyimide.

Electrical Insulation

Both polyamide and polyimide offer great insulation for electronic components. However, you should choose polyimide if you want to have electrical insulation to use in higher temperatures.

Polyimide is often used in things such as electrical components, cables, and wires in places where reliable insulation is needed at higher temperatures.

Chemical Resistance

Exposing polyimide to various chemicals won’t significantly degrade it. Therefore, you can use it even when it will be around harsh chemicals.

Although there’s chemical resistance with polyamide, some solvents and chemicals affect it negatively. Therefore, it’s best to choose polyamide for superior chemical resistance.

Cost Considerations

If you have a smaller budget, polyamide is a more affordable option. But, even though you're saving money now, it can cost you money and time in repairing your products. 

So, which should you choose? In general, you need to consider the requirements of your application. Although it offers more advantages, polyimide is more expensive.

Therefore, it's best to think about what you are creating and the environment in which you'll be using the application. Then, make your decision on which will work best for you.

Polyimide vs. Polyamide vs. FR4 in Electronics

What is FR4?

Now that we have looked at polyimide and polyamide, we are going to look at FR4 and compare them. FR simply means Fire Retardant, and the 4 simply differentiates it from the other materials.

It’s a fiberglass-reinforced laminated sheet made of epoxy and looks like a woven sheet made of cloth. FR also means the grade used for making the sheets. 

Advantages of FR4

·       Low-cost

·       Excellent dielectric strength

·       High ratio of strength-to-weight

·       Is lightweight

·       Moisture resistant

·       Relative resistance to temperature

·       Doesn’t absorb water

Disadvantages of FR4

• Unsuitable for Use in High-Frequency Applications

• Lower thermal tolerance

When You Should Avoid FR4

• Need great temperature resistance – If you’re using it in a high-temperature environment, use a different material

• Lead-free Soldering – The temperatures reached will be too high

• High-frequency signals – Fluctuations can happen and affect the signals’ integrity.

In conclusion, FR4 is a good low-cost material, but it’s not for every soldering project. If you aren’t sure whether it will work, it’s better to use either polyimide or polyamide.

Comparing the 3 Materials

When you are working on a soldering project, one of the most important things that you can do is to make sure the material you are using is appropriate.

Checking the quality of the material you are using is appropriate for the environment, and application will help ensure the success of your project.

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