With the rapid progress in electronics technology, different materials have been developed to adapt to the needs of various applications. Printed circuit boards, which are structures that electrically connect components, have also evolved to greater heights with the discovery of new processes, materials, and designs. One advancement in PCB technology is the development of flexible printed circuit boards using polyimide material. China polyimide PCB manufacturers have also invested in developing solutions and technologies to fabricate this type of PCB with high quality and efficiency. We will explore various topics related to polyimide flex PCB.
Polyimide PCB is a printed circuit board made of polyimide material. Polyimide is a lightweight, flexible material with excellent electrical properties and low thermal expansion. It is made from aromatic diamine and dianhydrides through condensation polymerization processes. Polyimide is a type of polymeric material that shows thermal stability in high temperatures with high chemical resistance. Polyimides also have a high glass transition temperature of greater than 250 degrees Celsius.
The first polyimide film, also called Kapton, was pioneered by DuPont company in the 1950s. It usually appears as a translucent, amber color film material. Polyimide circuit boards are mainly used in manufacturing flexible circuits.
Different polyimide flex PCBs can also come in various types based on the number of layers, complexity, and functionality:
Single-sided polyimide flex PCB has a conductive layer on one side of the PCB only with or without cover layers. Electronic components are mounted and interconnected on a single side.
Double-sided polyimide flex PCB has two layers of conductive tracks with a flexible substrate in between. This means that electronic components can be mounted on both sides.
Multilayer polyimide circuit board is a type of PCB with several layers of conductive patterns interconnected through vias and plated through holes.
Rigid-flex circuits are a combination of flexible and rigid substrates interconnected and laminated together. Mobile phones consist of flexible circuits that are connected to a rigid motherboard.
Polyimide may come in film structures which grants it certain advantages like bendability and flexibility. Even if polyimide circuit board is highly flexible, it also has very good tensile strength which means it is capable of bearing heavy load.
Polyimide PCB material is also resistant to corrosive chemicals. Its chemical structure does not degrade easily when interacting with solvents and substances. This property makes it even more suitable for medical applications.
Polyimide circuit board exhibits resistance to degradation even when subjected to high temperatures. The thermal stability of polymers is systematically measured using thermogravimetric analysis, wherein loss in mass is measured as a function of time at constant temperature. It can withstand 300 to 500 degrees Celsius, and it has the highest maximum working temperature among other polymers.
Polyimide circuit board also boasts of its favorable electrical properties such as low dielectric constant and good electrical insulation properties. It is particularly useful for high-voltage industrial applications. The low dielectric constant of polyimide circuit boards helps in maintaining signal integrity and in the reduction of unwanted capacitance between neighboring conductive traces.
Given the several advantages of polyimide circuit boards, different market sectors are using this type of material to produce highly functional devices. Here are the typical applications of polyimide flex circuits:
Medical devices require portable sensing devices with mechanical flexibility. Polyimide flex circuit has these advantages making it a popular material choice for medical applications. For instance, displacement sensors for biomedical devices contain polyimide PCB due to its easy integration with various electronics. The use of non-invasive portable systems for monitoring health signals in a real-time manner has a better advantage than bulky and wired systems.
Polyimide PCB is also widely used in commercial applications like computers, televisions, smartphones, and wearables, which require compact and light material. Smaller devices are made possible due to inherent low mechanical stiffness and thermal stability.
Electronic devices inside vehicles extensively use polyimide flex circuits due to their ability to be contained in small spaces of various geometries. Vehicles’ audio systems, cameras, controlling, and sensing devices have polyimide circuit boards.
The reduced weight and excellent thermal characteristics of polyimide PCB material make it a primary option for space electronics. Spacecraft electronics possess high-reliability components that can be satisfied by polyimide flex PCB. Flexible PCBs can substitute bulky wires and cables for non-planar dimensions for aerospace applications.
Now, let’s discuss the fabrication steps of polyimide printed circuit boards:
The polyimide material is laminated with copper foil which is carried out using a vacuum press at high temperatures to allow curing at a specified duration. The pressed laminate is again baked at a high temperature before moving to the next process. Layup is performed after lamination and moisture removal of prepreg.
The etching process is executed by applying a photoresist layer and exposing it to UV light through a masking process. The photoresist is immersed in a developing solution and a copper pattern is made by etching away the unwanted copper material.
Holes and vias are drilled into the polyimide PCB and subsequently plated to have electrical connections across the layers.
A solder-resistant material is then applied to the polyimide PCB to protect the copper from the oxidation process. A solder mask is applied to the insulating layers to prevent bridging and short circuits.
The silkscreen process involves printing information, such as component codes, locations, and references, on the PCB polyimide through a solder resist material.
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We implement strict control management systems in every process and function group to ensure high-quality products and services, such as ISO9001, TS16949, and ISO13485. Our staff are well-qualified and united, so we make sure the PCB is highly reliable when leaving our factory.
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Polyimide PCB, also known as polyimide printed circuit board, is a circuit board made from polyimide film. Polyimide is an advanced polymer containing imide groups. Polyimide material provides superior thermal stability, excellent chemical and mechanical stability, and high-temperature insulation.
Polyimide PCB material is an advanced polymer and a class of high-performance plastics, and this kind of material offers high-temperature resistance, excellent dimensional stability and dielectric properties.
From the perspective of a PCB manufacturer, we think there are two types:
Rigid polyimide PCB: it is commonly used in microwave and RF circuit boards. This kind of base includes such as Arlon 33N, 35N, 84N, 85N, AGC RF-30A, RF-35TC, etc;
Flexible polyimide PCB: it is usually used in applications that need to be bent. This kind of base includes Dupont Pyralux series, AP series, Panasonic Felios series, etc.
In general, the basic process of polyimide PCB design is as follows: pre-preparation → PCB diagram design → PCB layout → trace routing → routing optimization and silkscreen → network and DRC check and structure check → PCB production.
Let’s look at some of the benefits of using a polyimide PCB.
1) High-temperature resistance
2) Low dielectric constant
3) Low moisture absorption
4) Superior electrical insulation properties
5) Excellent thermal stability
6) Excellent chemical resistance
Board cutting → Drilling → Dry film and exposure → Copper etching → Solder mask printing → Components marks printing → Surface treatment → outline profiling → testing → Quality checking → Packaging & shipping
Polyimide PCBs are the circuits produced by polyimide materials. Generally speaking, there are two kinds of polyimide PCB boards: polyimide flex PCB and polyimide rigid PCBs. Kapton PCB is a circuit boards produced by Kapton which ithe polyimide material produced by Dupont company. So Kapton PCB is just a kind of polyimide PCBs.
Although most polyimide PCBs are flexible, there are also rigid polyimide PCBs which are produced by rigid polyimide PCB material, and they are usually used in microwave and RF PCBs. Such as Alron 85N, 33N, AGC RF-35TC, Rogers RO3003, RT/duroid 5880, etc.
Yes. Although most of polyimide printed circuit boards are flexible. But there are also rigid polyimide PCBs. For example, Arlon 33N, Arlon 35N, Arlon 84N, Arlon85N, Arlon HF-50high, Nelco N7000-2, Ventec VT-901, etc., these materials always have extremely high Tg 250℃, suitable for high reliable and long service life electroncis such as burn-in Boards, backplanes, electronics used aerospace, military, avionics, space industry.
PI PCB is short for polyimide PCB but usually only means flexible polyimide PCBs. So when we say “PCB PI”, it means the polyimide material used in flexible circuit boards. For rigid polyimide PCBs, we also call them PTFE PCBs or Teflon PCBs.
When designing polyimide PCBs, specific considerations must be taken into account.
For example, polyimide has a much higher thermal coefficient of expansion than other PCB materials, which can affect the overall size and shape of the board.
Additionally, polyimide has a much lower dielectric constant than other PCB materials, making it essential to consider how this will impact signal speed and integrity.
Thirdly, due to the unique parameters of this particular kind of plastic material, there are a lot of challenges in PCB manufacturing processes, such as lamination, drilling, copper plating and outline profiling. So a very experienced engineering and production team is needed.
Polyimide material is a special kind of plastic which is very difficult to degenerate. Proper manufacturing and disposal practices should be employed to reduce environmental risks associated with polyimide PCBs to minimize hazardous material release into the environment.
Furthermore, any polyimide waste should be recycled or disposed of under applicable laws and regulations.
Polyimide PCBs must be stored in a temperature, humidity-controlled and dust-free environment to prevent damage caused by contaminants, moisture and temperature changes. The shelf life of polyimide is usually 3-6 months. Special equipment, techniques and supportive tools will be needed in production.
The most standard finishing options for polyimide PCBs are as follows.
1) electroless nickel immersion gold (ENIG)
2) organic solderability preservatives（OSP)
3) electroless silver
4) tin plating
5) hot air solder leveling (HASL)
We can take a look at the following techniques for soldering p
