Special considerations must be taken when designing electronic hardware boards intended for use in severe environments to guarantee functionality and long-term durability. Extreme temperature swings, high humidity, dust, vibration, and other elements that hasten component deterioration can all be considered harsh environments. The essential actions to take when designing a pcb hardware design that has to endure challenging operating circumstances are described in this section.
Component Choice
Selecting components that can withstand the anticipated environmental conditions is the first stage. Seek components with ratings for high resistance to dampness, broad temperature ranges, mechanical toughness, and corrosion prevention. Because surface mount components don’t have exposed wire leads, they are typically more durable than through-hole components. Give industrial and military parts precedence before retail or consumer parts. For further defense against moisture, dust, chemicals, and temperature fluctuations, think about conformal coating electronics.
Temperature Control
In applications where temperature extremes are present, efficient thermal management is essential. To find possible hot spots during the design stage, use thermal simulation software. Optimize component and board layouts. Think about employing fans for forced-air cooling. For gadgets with a lot of power, choose heat sinks. Heat is removed by electrically insulating and thermally conducting materials such as phase transition materials or thermal pads.
Protection Against Moisture
Corrosion and other hazards are common in damp, harsh environments. By conformally coating the entire PCB, a watertight barrier is created. Other options include employing hermetically sealed enclosures or potting components in epoxy resin. Make sure that switches, connectors, and other openings are properly sealed. To absorb moisture inside enclosures, think about using desiccant packets. It is particularly crucial to apply a conformal coating or sealing to any exposed connectors, test points, or circuitry.
Resistance to Vibration
Over time, solder connection failures or component fatigue may result from mechanical vibration. Use methods like conformal coating or staking to reinforce solder junctions. Place reinforcement on connectors in strategic locations, such as strain reliefs. Use vibration-dampening materials to cushion mounting points. Steer clear of components with thin leads or fine pitch that are more vulnerable to vibration damage. For ruggedization, think about potting the entire board in epoxy.
Protection Against EMI/RFI
When using wireless radios or functioning near electrical noise sources, electromagnetic interference becomes more bothersome. Observe proper PCB layout techniques, such as keeping analog and digital grounds and traces separate. Use conformal coatings, gaskets, or conductive enclosures to add EMI shielding. High frequency noise is filtered by ferrite beads on cables. Any sensitive signals should be connected via a shielded wire.
Design for Maintainability
Equipment that is placed in dangerous or distant areas needs to be serviceable. Add status indicators and test points. It is simple to replace components in designing embedded system. Give field-replaceable connectors some thought. All parts, connectors, and test locations should have legible labels. Add design file and schematic documentation. Schedule local user interface or over-the-air firmware/software updates.
Testing in the Environment
Before completing production, subject early prototype designs to representative environmental stress testing. It reveals areas of weakness. Temperature cycling, thermal shock, vibration, humidity exposure, salt fog corrosion, and dust ingress are examples of common tests. Keep an eye out for any malfunctions or poor performance. Before mass producing, make adjustments to the design in light of test findings.
Best Practices for PCB Layouting
Adhere to layout recommendations tailored for ruggedized boards. Reduce component spacing and trace lengths for smaller, less vibration-prone designs. For power and ground connections, use traces that are broad, short, and straight. Separate the digital and analog signals. Position decoupling capacitors in proximity to the ICs’ power pins. In high current areas, think about using thicker trace widths or redundant vias. mechanically and thermally stable heat-producing elements.
Design of Enclosures
The PCB assembly is supported and shielded by the enclosure. Select a material that is appropriate for the application, such as composite, metal, or plastic. Think about dust and water resistance ratings for ingress protection (IP). Add mounting locations, connectors, status lights, and any other required interface elements. Provide modular subassemblies whenever possible to facilitate simple assembly and disassembly. Apply conductive coatings inside to add EMI shielding.
Examination and Accreditation
Before deploying the design, make sure it has undergone extensive testing to verify its resilience to the environment. In a lab, replicate expected field circumstances and stress levels. Adherence to industry, application, or regulatory requirements may necessitate certification. IEC/EN/UL/CSA standards for electrical safety, EMC emissions and immunity, shock and vibration resistance, moisture resistance, and other environmental tests are examples of common certifications. Before production, resolve any concerns.
Selection of Materials for Conformal Coating
There are numerous conformal coating materials available, each with unique qualities appropriate for a range of settings and uses. Epoxy-based coatings tolerate a wide range of temperatures and have strong adhesion and moisture resistance. They can’t be fixed as easily as alternative solutions, though. Epoxy takes longer to cure than acrylic coatings, which are more flexible and facilitate simpler repair work. However, its resistance to heat and moisture is marginally weaker. Urethane coatings offer excellent protection against chemicals, moisture, and severe temperatures together with flexibility. Additionally, they are easier to fix than epoxy. Among the common conformal coating materials, silicone has the lowest moisture barrier qualities but is exceptionally flexible and heat-tolerant. Finding the proper material requires weighing the demands of repair or rework against the particular environmental conditions.
Design for Production
Once the design is confirmed, attention turns to production and manufacturability. Take into account elements such as automated assembly, quality assurance inspections, and replacement/repair procedures. Reduce the number of components and placement challenges. Utilizing prefabricated subassemblies, modular designs expedite assembly. Provide fittings and jigs to help with fine-pitch component positioning. Board sizes should be optimized for pick-and-place devices. Incorporate test point access and fiducial markings. Untrained workers can build and service units in the field with the use of comprehensive documentation and process instructions. Standardize on connectors, fasteners, lights, and other interchangeable components. Make plans for tracking revisions and serial number traceability. Early problem detection through design reviews with the manufacturing and service teams lowers costs and increases yields.
In summary
By adhering to these best practices, PCB hardware board design can be made to endure challenging operating conditions for prolonged periods. For electronic equipment to remain reliable over time in challenging applications, careful component selection, heat management, moisture protection, EMI shielding, ruggedization techniques, and testing are essential. Even in difficult circumstances, PCBs may function dependably with the correct design process and validation testing.
