Flexible PCB is defined as the arrangement pattern of integrated circuits and components using flexible materials. Here, the same components used to produce rigid printed circuit boards can be used to manufacture these flexible electronic components, but they should allow for the flexibility of the circuit board during their application.
Some of the advantages provided by flexible PCBs include: light weight, high reliability, high ductility, and space saving. However, inventors/designers must be prepared for their complexity and complexity.
In addition to designers being responsible for the mechanical complexity associated with flexible circuits, there is also no significant difference between flexible PCBs and rigid boards during the design phase. For example, if a flexible PCB is bent beyond its performance, it may tear during installation.
Therefore, creating a mechanical model of a PCB and testing it is crucial to cooperate before conducting electrical design. In addition, this will include any misalignment, maintenance, and ergonomic testing of the installation. In addition, designers need to understand the different available flexible circuits and their working principles.
Types of flexible PCBs
According to its application, there are different types of existing flexible PCBs. Among them, flexibility, high-density interconnect (HDI) flexibility, and rigid flexibility are the most prominent.
These PCBs have flexibility and vibration resistance, making them unique and unique. They are the most common flexible versions of existing rigid PCBs. Their additional functionality comes with the usual repeatability, high density, and reliability that rigid PCBs have already provided.
The ability of flexible circuits to adopt three-dimensional configurations is the main advantage of rigid PCBs. One of the most common applications for flexible PCBs is to replace wiring harnesses.
Rigid-Flex PCB
These PCBs are a combination of flexibility and rigidity. Although some unique capabilities have been added that cannot be possessed by flex and rigidity when separated, they provide the best of the two structures. For example, a series of rigid PCBs originating from typical rigid flexible structures will be connected through integrated flexible circuits. Therefore, designers can greatly improve their circuit design capabilities by supplementing flexible areas with rigid components.
High Density Interconnection (HDI) Flexible PCB
When there are not enough options for typical flexible circuits, HDI PCBs come into play by combining fine-grained functions such as better layout, structure, and design with micro through holes. In addition to the above functions, other functions include high-density flexible circuits, enhanced functionality, and smaller overall dimensions.
HDI technology provides better electrical performance, allowing for the use of advanced IC packaging and the use of thinner and more reliable materials.
Advantages of Flex circuits
As for the replacement of ribbon cables or discrete wiring, customized and repeatable wiring provided by flexible circuits is distributed throughout the entire component. Due to their higher reliability, they can reduce maintenance calls.
Polyimide is a dielectric layer that covers and protects the circuit, rather than a simple sales mask. The flexible board uses this layer to cover the conductors of the flexible circuit. Manufacturers use other substrates and covering materials to handle a wider range of harsh environments and environmental conditions.
Flexible plates can withstand long bending cycles, although they can be very thin to resist and withstand millions of bending cycles, appropriate design materials can be used to strengthen these plates. This is to ensure that there is no interruption when transmitting power and signals.
Flexible circuits with high ductility and low quality have excellent advantages when facing high acceleration and/or vibration. Under the same working conditions, the impact and stress of rigid PCBs and their solder joints and components are much greater than the impact faced by solder joints on flexible PCBs
The advantages of flexible circuit board make it very suitable for many applications in medical, consumer electronics, military, aerospace, industry, automobile, transportation and communication fields.
Types of flexible PCBs
According to its application, there are different types of existing flexible PCBs. Among them, flexibility, high-density interconnect (HDI) flexibility, and rigid flexibility are the most prominent.
These PCBs have flexibility and vibration resistance, making them unique and unique. They are the most common flexible versions of existing rigid PCBs. Their additional functionality comes with the usual repeatability, high density, and reliability that rigid PCBs have already provided.
The ability of flexible circuits to adopt three-dimensional configurations is the main advantage of rigid PCBs. One of the most common applications for flexible PCBs is to replace wiring harnesses.
Rigid-Flex PCB
These PCBs are a combination of flexibility and rigidity. Although some unique capabilities have been added that cannot be possessed by flex and rigidity when separated, they provide the best of the two structures. For example, a series of rigid PCBs originating from typical rigid flexible structures will be connected through integrated flexible circuits. Therefore, designers can greatly improve their circuit design capabilities by supplementing flexible areas with rigid components.
High Density Interconnection (HDI) Flexible PCB
When there are not enough options for typical flexible circuits, HDI PCBs come into play by combining fine-grained functions such as better layout, structure, and design with micro through holes. In addition to the above functions, other functions include high-density flexible circuits, enhanced functionality, and smaller overall dimensions.
HDI technology provides better electrical performance, allowing for the use of advanced IC packaging and the use of thinner and more reliable materials.
Advantages of Flex circuits
As for the replacement of ribbon cables or discrete wiring, customized and repeatable wiring provided by flexible circuits is distributed throughout the entire component. Due to their higher reliability, they can reduce maintenance calls.
Polyimide is a dielectric layer that covers and protects the circuit, rather than a simple sales mask. The flexible board uses this layer to cover the conductors of the flexible circuit. Manufacturers use other substrates and covering materials to handle a wider range of harsh environments and environmental conditions.
Flexible plates can withstand long bending cycles, although they can be very thin to resist and withstand millions of bending cycles, appropriate design materials can be used to strengthen these plates. This is to ensure that there is no interruption when transmitting power and signals.
Flexible circuits with high ductility and low quality have excellent advantages when facing high acceleration and/or vibration. Under the same working conditions, the impact and stress of rigid PCBs and their solder joints and components are much greater than the impact faced by solder joints on flexible PCBs
The advantages of flexible circuit board make it very suitable for many applications in medical, consumer electronics, military, aerospace, industry, automobile, transportation and communication fields
The use of flexible circuits
Flexible circuits are shaped by designers to fit any other type of PCB in the region. Although flexible circuits have their own advantages, some people can think of them as a hybrid combination of circular wires and ordinary PCBs. Someone can maintain the conventional PCB density, accuracy, and repeatability, and with the help of flexible circuits, still achieve infinite freedom in packaging geometry.
Usually, wiring harnesses are replaced by flexible circuits. In one operation, this allows a single flexible circuit to shift several cables, hard boards, and connectors. Because it bundles them together and eliminates the need for color coding lines, components will proceed faster than usual. The possibility of rejection will decrease during the use of faults and assembly processes, and the production level will increase with the decrease in installation costs.
When flexible, the repeatability of wire routing increases the replacement of wiring harnesses by circuits. During wiring, this can eliminate errors, thereby reducing rework, testing time, and rejection. Due to the fact that circular wires cannot carry more current and dissipate heat better than flat foil conductors with the same cross-sectional area, the connection is more secure. When designers decide on a more uniform conductor pattern in flexible circuits, they will have better control over noise, crosstalk, and impedance.
In addition, space and/or flexible circuits can reduce the weight of traditional wiring to approximately 75%. Compared to using wiring harnesses, flexible circuits have lower repetition costs. Compared to hard boards, the cost of replacing and repairing flexible circuits is much lower because they are more resistant to impact and vibration. However, surface mounted components can be easily installed on flexible boards by placing adhesive reinforcing ribs in the required area.
Advantages of rigid flexible circuits
Due to the rigid flexible combination circuit replacing the maximum number of components, it is beneficial to use it when looking at the total cost of the entire device. The combination of rigid and flexible circuits provides maximum vibration resistance and capability, as they can mix the best resistance in the rigid area with the elastic flexible area, and can also install surface mount components on both sides of the circuit board. When installing high-quality components, this is the best combination option as it can provide a better and smoother transition between flexible and rigid areas while retaining its advantages.
Defining appropriate layers for multi-layer PCBs is one of the most important preliminary designs. For large and dense PCBs with many pin count BGAs, this is very important, especially when the stacking of standard laminates is insufficient in terms of performance goals and costs. If designed properly, HDI stacking can effectively replace a large number of layers and provide low cost and higher performance.
For circuit boards with high pin count BGA, there are three types of pasting. They include; Sequential lamination with buried and blind holes, stacking with micro through holes, and standard lamination with through holes. Among these three, the stacking of micro through holes is mainly used by HDI boards, as it has many advantages:
The mode of micro through holes can use more efficient ones. In this way, more wiring channels can be opened, thereby reducing the number of layers.
For high-density circuit boards, it can provide the lowest cost.
Fewer layers and higher wiring density result in smaller sizes of through holes and wiring.
Micro through-holes are the only practical method for designing several large BGAs with spacing less than 0.88mm.
Appropriate definition of superposition
They contain materials suitable for procedures that must comply with RoHS standards.
Lower cost, providing updated materials to achieve higher costs. Performance and they may not be suitable for other lamination types.
The HDI PCB layer defined by the PCB manufacturer is 16 layers and the overall board thickness is only about 66 ± 7 mils. They have laser drilled micro through-holes and require sequential construction (SUB).
Cost impact
Generally speaking, although rigid PCBs are cheaper than flexible circuits, the cost increases as the number of layers increases. Therefore, in order to minimize costs, some factors must be considered. For example, using a four layer circuit may be more expensive compared to two double-layer circuits.
Supporting flexible circuits may reduce overall efficiency costs due to other factors. For example, folding flexible circuits can save layers and space. Depending on the specific situation, time investment in project evaluation may lead to significant savings.
