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Understanding Industrial PCBs
What Are Industrial PCBs?
An industrial PCB is a circuit board specifically designed for industrial applications, such as high-voltage motor controllers and control electronics for manufacturing equipment.
Compared to standard PCBs, industrial boards differ in three areas:
- Operating Environment: Industrial PCBs are built to withstand extreme temperature swings (-200°C to over 300°C), corrosive chemicals, high humidity, vibrations, mechanical shock, high voltages, and more.
- Lifespan: These boards can deliver high performance and reliability for 10–15 years.
- Criticality: Industrial boards are critical for safety applications, as vital systems rely on them. If they fail, the consequences can be severe.
According to IPC standards, industrial PCBs fall into the class 3 category, while standard PCBs fall into class 1 or 2. Like standard PCBs, industrial PCBs come in several types:
- Single-sided PCBs: These boards have one copper and substrate layer, forming a simple circuit.
- Double-sided PCBs: These boards have one substrate with two copper layers, one on each side, forming a moderately complex circuit.
- Multilayer PCBs: These have three or more copper layers, interconnected using vias, that form a complex circuit.
Multilayer PCBs
- Rigid PCBs: As the name suggests, rigid PCBs have rigid substrates that prevent twisting or bending.
- Flexible PCBs: These boards feature flexible substrates, allowing them to bend and transform into various shapes without damaging the circuit. They are also lighter than their rigid counterparts.
- Rigid-flex PCBs: These boards combine rigid and flexible sections to form one continuous circuit, offering both flexibility and structural integrity.
- High-frequency PCBs: Designed to operate in RF and microwave frequency ranges, these boards require careful consideration of power dissipation, dielectric thickness, and dielectric constant to ensure reliable signal transmission.
- Metal-base PCBs: Typically using laminated aluminum as the base, these boards offer high thermal conductivity and mechanical strength.
Applications of Industrial PCBs
Applications of Industrial PCBs
Industrial PCBs are used in the aerospace, automotive, energy, marine, manufacturing, defense, and other industries with the following use cases:
- Building control: Equipment like elevators, HVAC, lighting control, smart buildings/homes, control panels and gateways, ventilation systems, and passage controls require industrial boards to operate reliably.
- Embedded computers: Devices like robots, vending machines, charging stations, and parking meters require effective heat management, which is facilitated by industrial PCBs.
- Motion actuators: Actuators in applications like garbage trucks, excavators, and hydraulic control packs subject PCBs to extreme vibrations and high temperatures. These applications often use rigid-flex and multilayered industrial boards.
- Industrial imaging: Advanced imaging systems need high-speed, high-frequency HDI industrial PCBs to handle high-speed signal transfer and digital processing.
- Sensors: Industrial PCBs in sensors measure parameters such as temperature, vibrations, light, and pressure, and they require high durability in order to withstand harsh conditions.
- Motor control: Machines like robots, conveyor systems, industrial pumps, and fans have large motors that require high-density, rigid-flex industrial PCBs for effective control.
- Marine electronics: Navigation systems, satellite and radio communication, radar systems, and engine control units in marine environments all depend on industrial PCBs.
- Personal protection equipment: Circuit boards in welding helmets, respiratory helmets, and hearing protection devices require small sizes, noise cancellation, and signal integrity to provide the required performance.
- Test and measurement devices: Oscilloscopes, multimeters, and RF/power/radio signal analyzers rely on industrial PCBs for accurate performance.
Industrial boards ensure these devices remain operational for extended periods and sustain reliable performance with zero downtime, even when exposed to challenging conditions.
The Industrial PCB Manufacturing Process
The Industrial PCB Manufacturing Process
Step 1: Design and Layout
While the design process is not part of manufacturing, it’s critical for building a proper industrial PCB. It gives fabricators time to carefully lay out the circuit plan and ensures the following factors are taken into consideration:
- Derating rules: Component derating involves lowering the operating values of PCB components below the maximum values specified in the datasheet. This includes power levels (voltage and current), thermal stress, chemical stress, and mechanical stress. Derating provides a sufficient margin against variations, such as voltage spikes, to ensure the PCB remains functional without failure.
- Redundancy: Avoiding single points of failure is essential, which is why industrial PCBs should incorporate redundancy through extra traces, backup pathways, and automated failovers.
- DFM analysis: Rigorous Design For Manufacturing (DFM) analysis is crucial, especially when checking for issues like annular rings, thermal relief connections, and trace widths.
- Layout methods: Efficient thermal management techniques, edge control structures, stitching vias, and thick traces should be considered to handle high currents with minimal resistance.
- Standards validation: Design development of industrial PCBs should adhere to relevant standards, such as IPC 2220 series and MIL-PRF-31032, for defense equipment circuit boards.
- Early simulation: Before manufacturing, tools like COMSOL, Altair, Siemens, or Ansys should be used to simulate the PCB’s operating environment. This helps identify potential issues under various thermal, electrical, and vibration conditions.
The circuit design process requires CAD tools like Eagle and Altium Designer to encode the design rules and EDA tools for circuit simulation and analysis. When working with WellPCB to manufacture your printed circuit boards, you can either send us your design files or let us handle the entire design process for you before manufacturing.
Step 2: Material Selection
Once the design files are ready, the next step is to select the most suitable materials for the board. This selection process considers various factors, including:
- Dielectric constant
- Dielectric thickness
- Thermal conductivity
- Environmental conditions
- Dissipation factor
- Coefficient of thermal expansion
The most popular material for industrial PCBs is FR4, chosen for its mechanical strength and durability. However, it has a lower thermal conductivity than ceramic boards.
Ceramic and composites like Teflon (PTFE) and polyimide are better for harsh environments due to their resistance to chemicals, moisture, and other environmental factors. When making high-frequency industrial PCBs, materials such as Rogers and Teflon are preferred because of their low loss tangents and dielectric constants, which minimize signal losses. However, these materials are more expensive than FR4 and are only used when necessary.
For industrial boards exposed to extreme mechanical shocks and vibrations, metal cores are the optimal choice. As metal dissipates heat quickly, it is also suitable for LED and power electronic boards.
Step 3: Printing and Etching
The next step is to print the circuit on the board, which can be done via photolithography or laser direct imaging (LDI).
Photolithography uses a high-precision photoplotter to create circuitry images from the Gerber Files onto a film, which acts as a template for defining the circuit’s traces on the copper layer bonded to the substrate. A photoresist is first applied over the copper, followed by the film (photomask) above it. UV light is then shone on the photomask, hardening it.
LDI is more accurate and user-friendly than photolithography, as it’s a computer-controlled process that defines the circuit pattern directly above the photoresist.
This method is used for its high accuracy, which is critical for industrial PCBs to ensure circuit reliability. LDI also enables the transfer of complex designs and offers a higher throughput.
Once the design hardens on the photoresist, corrosive chemicals are applied to etch unwanted copper on any sections not covered by the hardened photoresist, leaving only the circuit pattern.
The dry film is then removed, and the process is repeated to create the other copper layers.
Step 4: Laminating and Curing
Each copper layer first undergoes AOI before it is laminated to the rest, forming a “sandwich” with a prepreg for insulation in-between.
The “sandwich” for multilayer industrial PCBs includes dedicated power and ground planes on the outer sections, with some designs incorporating them in the inner planes as well.
The specific arrangement depends on the number of layers in the board.
After carefully arranging the stack, the layers are laminated using heat and pressure to cure the prepreg and permanently bond them into a single board.
Step 5: Drilling and Plating
For single and double-layer PCBs, drilling is relatively straightforward because it primarily involves creating through holes, which are then plated for through-hole component mounting.
Multilayer boards present a greater challenge due to buried and blind vias. Buried vias must be drilled and electroplated to join the respective internal layers before laminating the entire stack to form the board.
Blind vias are exposed to the outer layers on one side so they can be drilled after lamination and curing.
However, this drilling must be done carefully to avoid any contact with the underlying layers.
Drilling can be performed using either mechanical or laser drills, with the latter being more accurate and suitable for thin 3- to 6-mil vias.
After drilling, chemical and mechanical processes are used to clean the holes and remove debris.
Once clean, the holes are electroplated to line them with copper, creating electrical connections with the internal circuits.
This electrochemical deposition process must be strictly regulated to control the amount of copper deposited on the hole walls.
Some boards require copper-filled vias to improve conductivity, while others are filled with non-conductive materials to prevent contaminants from getting in.
Step 6: Testing and Quality Control
Once the solder mask and surface finishes have been applied, the complete board undergoes various electrical tests to ensure it can handle the expected power loads. These tests include:
- In-circuit testing (ICT) using either a bed of nails or flying probes
- Burn-in testing
- Solderability testing
- Contamination testing
- Impedance control testing
The boards also undergo thermal and environmental testing, followed by inspection via AOI (Automated Optical Inspection) and X-ray, which are ideal for checking the inner layers of multilayer boards. These additional tests help identify any flaws before packaging and delivery.
All testing and inspection procedures are carried out in accordance and compliance with relevant standards, such as UL and IPC (class 3).
Benefits of Industrial PCBs
Benefits of Industrial PCBs
Enhanced Durability and Reliability
The primary advantage of industrial PCBs is their durability and reliability.
These boards can function effectively for 10–15 years in their respective application areas, often matching the entire service life of the product they support.
The choice of materials and build quality make industrial PCBs resistant to harsh operating environments, which extends their lifespan.
For example, polyimide can withstand temperature swings from -270°C to 350°C, making it ideal for space and aviation applications.
Customization and Flexibility
Industrial PCBs can be customized to meet any industrial application by modifying the circuit design and selecting appropriate materials.
Flexible substrates can also be used to fit boards into tight spaces.
For instance, sensor PCBs in aviation and aerospace applications often use flexible or rigid-flex materials to reduce their size and weight.
In contrast, factory SCADA and IoT systems typically use rigid boards, as size and weight are less critical.
Cost-Effectiveness
Though industrial PCBs are more expensive to design and build, especially considering the materials used, their long-term cost is lower than that of standard boards due to their extended lifespan and reliability.
Standard boards need to be replaced several times over the same 10- to 15-year lifespan that industrial boards provide.
This results in higher purchasing costs and increased downtime, making standard boards more costly in the long run.
Industry Innovations and Trends in Industrial PCB Manufacturing
Recent Technological Advancements
Sustainable PCB Manufacturing
Material selection is a crucial part of the industrial PCB manufacturing process, and recent advancements are shifting toward sustainability.
More eco-friendly materials like ceramic and metal are increasingly favored over FR4 and high Tg FR4, which are not recyclable and contribute to plastic waste.
When FR4 is used, manufacturers are opting for halogen-free variants, which do not emit harmful gasses when burned.
Miniaturization
The ability to build multilayer boards with up to 50 layers has enabled the creation of compact HDI PCBs that house multiple components and features in a tiny space, which is ideal for miniaturized industrial electronics.
High-Power Boards
High-power boards operate at higher voltages, such as 48V, and support energy generation applications, most commonly for solar power systems and electric vehicles.
Future Trends to Watch
Increased Use of Flexible PCBs
Flexible circuit boards will become increasingly prevalent as they enable more compact industrial electronics.
Rigid-flex PCBs are also likely to become more common as they combine dense, multilayer designs with flexible sections, allowing them to fit around various objects.
A flexible PCB
3D Printing
Current PCB manufacturing methods use etching to produce copper circuits, which is wasteful and hazardous due to the corrosive chemicals used.
As 3D printing is an additive process rather than subtractive, it doesn’t require any chemicals and is therefore less wasteful and non-hazardous.
As such, 3D printing PCBs is likely to become more common in the future.
AI and IoT Integration
Increasingly used to enhance various manufacturing processes, AI and IoT are expected to make industrial PCB fabrication more efficient through increased automation.
This will lead to cheaper manufacturing with fewer defects, reworks, and customer returns.
Partner with a trusted manufacturer for your industrial PCB
To recap, design and material selection are the most important steps in industrial PCB manufacturing because they lay the foundation on which the board is built.
The other steps, while relatively standard, involve stricter quality control to ensure the board meets industrial requirements.
When built correctly, these PCBs can function for at least a decade, resulting in lower costs overall.
At WellPCB, we carefully optimize the entire industrial PCB manufacturing process for maximum durability and reliability.
Our commitment to quality is reflected in our ISO 9001:2015 and 14001:2015 certifications and adherence to all IPC and RoHS standards.
Contact us today to get started with your industrial PCB manufacturing project.
We can confidently deliver prototypes and small batches in 5–7 days, or 48 hours with our faster lead time option.
