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The Future of Polyimide PCB- A Comprehensive Perspective

What is Polyimide pcb ?

Did you know that the first polyimide discovered was in 1908 by Bogart and Renshaw? Or that polyimides have been mass produced since 1955? Polyimides come in orange, yellow, and amber colors or as transparent materials, and are highly demanded due to their strength and flexibility.

These are high-performance, incredibly strong synthetic polymers made of imide monomers containing two acyl groups (C=O) bonded to nitrogen (N). They have high temperature performances ranging 400-500°C, making them incredibly heat resistant.  They come in various forms: films, membranes, coatings, nanofibers, fibers, adhesives or foams.

Thermoset Polymers

A polyimide is a thermoset polymer (a polymer obtained by curing or irreversibly hardening processes, or simply stated it cannot be melted again). This makes it resistant to warping.

Since polyimides are strong; they are slightly more unyielding than other similar materials. This does not mean they are not flexible or cannot be bent: it just requires extra application of force.

Physical Attributes of Polyimides

Generally yellow in color, the hue depends on the chemical structure, polymerization method, and monomers. Those prepared from highly purified aromatic dianhydrides may be highly colored. Distilled or sublimed, m- and p-phenylenediamine form colorless crystals, which melt in solution or on exposure to air. Polyimides can also be translucent or opaque.

Chemical Properties of Polyimides

Polyimide PCB

Polyimides—PIs resist most chemicals including halogenated solvents, alcohols, and hydrocarbons. They have strong creep resistance properties, i.e., the tendency of a material to slowly deform over a long period of exposure to high levels of stress. Due to their strength, they can replace high performance materials such as metals in structural applications. They also stay stable under variable frequencies, temperatures, humidity and other environmental conditions. Here are some key chemical characteristics:

Dielectric

Polyimides as dielectric materials, i.e., they are non-conductors or poor conductors of electricity. High-temperature dielectrics are key components to developing complex power and electronics systems that operate under extreme conditions.

Flexible

Polyimide composites increase the material’s suppleness. They are used to produce flexible and rigid-flex (a combination of flexible and rigid boards) printed circuit boards because the material is exceptionally flexible.

Tensile Strength:

Despite its flexibility, polyimide materials are very strong and crawl resistant, such materials are resistant to warping over time. Therefore they are great choice for applications requiring physical durability.

Thermal Stability:

Polyimides remain stable when exposed to a wide range of temperatures. They support operations at extreme temperatures up to 260 degrees Celsius. They also are good thermal conductors and can withstand thermal damage during manufacturing and/or repairing.

Chemical Resistance:

Since polyimides are chemically stable, they can be subjected to many corrosive chemicals without being negatively affected, making them a key component in applications that include exposure to harsh chemicals.

Durability:

Polyimide PCBs effectively resist high amounts of physical stress. They maintain their shape despite changes in physical and thermal conditions. Thus they can be used for applications involving harsh environments and field repairs.

Uses of Polyimides PCB

Polyimides are created as thermosets or thermoplastics and are used as laminating resins, insulating coatings, plastics, films, and high temperature structural adhesives. They have a wide use in electronics, automobiles, and aerospace, to replace metals (even steel) and glass, in many industrial applications. They also perform well under harsh conditions, such as elevated temperatures. Polymer materials are increasingly been utilized to enhance standards of living through textiles, household appliances, insulation materials in construction and industry, materials for optoelectronics, medical implants, the formation of nano-sized films and much more.

Applications of Polyamide PCB Material

Though natural and synthetic polyamides are both used in a wide range of applications their leading use is as printed circuit boards. These materials can be found in vehicles, clothing and consumer products. Polyamide is used to create flexible and rigid-flex PCBs, both of which have gained momentum recently and are expected to expand exponentially by 2027.

The Polyimide PCB

Since polyimide is a flexible material, it is used for flex and rigid/flex boards, while FR4 (made of woven glass and reinforced epoxy resin) is used mainly for rigid PCBs. Polyimide is actually stronger and more durable than FR4. These boards have excellent temperature endurance and strength. The manufacturing, sometimes requires a variety of materials which affects its types and application.

Types of Polyimide PCBs

There are basically four types of Polyimide PCBs

1. Pure polyimide or 2nd generation polyimides:

This is the simplest polyimide PCB or pure polyimide PCB. It is it extremely stable (lacking additional features such as brominated flame retardants) and flexible enough to use in different electrical and communicating devices. It is commonly called polyimide flex PCB, due to its flexibility.

2. 3rd generation polyimide:

This is an evolved version of the first enhanced to make it more flammability resistance, so it can actually stop transmission of accidental electric fires. Though it lacks the thermal stability of pure polyamides, it is easy to manufacture, and goes through a faster production process than any other polyimide flexible PCB, thus laying way for bulk production.

3. Filled polyimide:

Filled polyimides are similar to multilayer PCB and comes with more than one filler materials, to lower the resin shrinkage. Printed circuit boards may become frail and develop crack downs during the drilling and curing proceedings due to resin shrinkage. Shrinkage resistance maximizes long-term usage of filled polyimides.

4. Low-flow polyimides:

Low-flow polyimides do not have the flexibility of the standard PCBs, and are called rigid polyimide PCB. This rigidity is required when PCB stiffness and strength is crucial, especially for challenging conditions. Where traditional flexible PCBs fail, low-flow polyimides withstand many adverse situations.

PCB Market Dynamics – Opportunities for Growth of the PI PCB Industry

Flexible printed circuit boards – FPCBs are in rising demand for smartphones and cellular devices; also LCD displays, rechargeable batteries, and connectivity antennas. Demand from automotive industry, defence and aerospace is increasing for the forecast period till 2027. As IoT catches on in more consumer electronics applications, FPCBs’ popularity and market domination will continue growing.

New Venues for Polyimide PCBs

With new focus on polymer plastic solar cells, and foldable or rollable smartphones, investors in FPCB will find many opportunities for great returns on investments. The use of FPCBs flex circuits in electronic wearables is also expected to increase. Disposable electronics such as single-use phone chargers or the chips found in print cartridges will upsurge market growth over the next few years. FPCB manufacturers will find growth opportunities in the healthcare sector such as digital pregnancy tests (also a disposable electronic).

ROHS and REACH Compliances enhance (Polyimide) FPCB Use in Disposable Electronics

There are concerns regarding the leakage of harmful chemicals into the environment from these single use electronics, but RoHS and REACH compliances reduce the number of potentially harmful chemicals in electronics.

Restriction on Hazardous Substances or RoHS compliance certifies that a product has been tested for 10 banned substances by a third party to check that confirmed levels of the substances are below the RoHS threshold. The restricted substances must be within the range of 1,000 ppm except cadmium, which has a limit of 100 ppm. These substances are:

  • Cadmium
  • Hexavalent chromium
  • Lead
  • Mercury
  • Benzyl butyl phthalate (BBP)
  • Dibutyl phthalate (DBP)
  • Bis(2-ethylhexyl) phthalate (DEHP)
  • Diisobutyl phthalate (DIBP)
  • Polybrominated biphenyls (PBB)
  • Polybrominated diphenyl ethers (PBDE)

Registration, Evaluation, Authorization and restriction of Chemicals (in short REACH) requires written disclosure of 209 substances of very high concern (SVHCs) in products and packaging through third-party lab tests.

Disposable electronics are likely to capture global markets and not be environmental hazards because they have delayed breakdown speeds. Some, such as circuits take 10,000 years to decompose. This means that the rate of waste release is extremely low. Lead and mercury were widely used in electronics from the past, and lead solder is still being used commercially in the US. Harmful environmental effects from electronic waste will be more likely from older electronics or countries that do not follow RoHS and REACH regulations.

Drawbacks in Polyimide PCB Mass Adoption

Flexible PCBs have a high initial cost associated to production. Until cheaper methods are initiated, this will remain a massive roadblock to rapid adoption of FPCB technology. Research favors a suitable outcome as it is expected that some global FPCB manufacturing giants such may make strategic acquisitions and/or collaborations causing significant progress in the market.

Conclusion

The adoption of multilayer FPCBs and use of rigid-flex FPCBs are both increasing exponentially. This simple fact could be the reason for major upsurges in the global flexible, polyimide printed circuit boards market. As a demand for automation in daily appliance, IoT and robotics increases there will be several niches for highly profitable growth over the next decade. Furthermore as fabrication technology and circuit material continue to evolve, the market will grow. This is a great time to invest in a technology that has emerging uses and great chances for high returns. If you have not already considered it, now would be the time to do so. The market is lucrative, find your niche.