A Step-by-Step Guide to Mounting Circuit Boards
Circuit boards, also known as printed circuit boards (PCBs), are thin boards that hold chips and other electronic components. Properly mounting circuit boards is crucial for building electronic devices that function correctly. This guide will walk you through the key steps for securely mounting circuit boards in your projects.
Gather Your Materials
You will need the following materials:
- Circuit board
- Standoffs
- Screws
- Nuts and washers
- Mounting brackets (optional)
- Soldering iron and solder
- Wire cutters/strippers
- Multimeter
Make sure to choose hardware designed for mounting circuit boards such as nylon or brass standoffs. You’ll also want screws that fit through the mounting holes on your circuit board.
Prepare the Enclosure
First, plan where your circuit board will be positioned inside the enclosure. Clean the area thoroughly to remove any debris. Insert standoffs into the chosen mounting points and twist them in place by hand or use a wrench to fully tighten them.
Position them according to the circuit board holes so the board will align properly when placed. Having standoffs already secured in the case makes mounting easier.
Modify the Board (If Needed)
Some modifications may be required to mount the board securely:
- Cut traces on the solder side to disconnect ground planes going to mounting holes. This prevents short circuits.
- Drill new holes if the existing ones don’t line up with your standoffs. Place tape over the area first to prevent cracking.
Attach Mounting Hardware
With the standoffs inserted into the enclosure, carefully place the board onto them, lining up the holes. The standoffs should hold the weight easily without flexing.
On the component side of the board, add a washer and nut onto each protruding standoff screw. Tighten down gently using your fingers first then finish with a wrench. Don’t over tighten or you may damage the board. Ensure the board sits evenly without bending.
Mounting Options:
- Standoffs and screws – Simple yet secure method. Allows access to both sides of the board.
- Adhesive mounting pads – Easy option for lightweight boards. Allows you to mount to irregular surfaces.
- Mounting brackets – Good for larger boards. Brace along the edges with brackets screwed into place.
Solder Components and Connections
With the board physically mounted, you can now solder components onto it and make wiring connections:
- Solder components like ICs, capacitors, etc. onto the topside according to circuit diagram
- Trim excess leads after soldering each component
- Heatshrink wire connections to prevent shorts
- Use cable clamps or ties to neatly route wires
Double check your solder connections with a multimeter for quality. Faulty joints can cause problems. Reflow any suspicious ones.
Test and Troubleshoot
Before closing up the enclosure, power up the board and test operation. Observe voltage levels, clock signals or other outputs to verify functionality. The data sheet is key for determining expected results.
If issues are found:
- Check power connections and polarity first
- Inspect solder joints under a magnifier for bridging or cold joints
- Probe test points to verify chip inputs/outputs
- Swap suspect components like ICs with known working ones
- Consult board schematics regarding circuit operation
Thorough troubleshooting at this stage prevents headaches later.
Complete Assembly
Once fully functional, finish up by neatly dressing any loose wires with ties, foam, or brackets to prevent wire movement stress. Double check screws and standoffs to ensure they are snugly tightened. Verify clearance space around the board for air ventilation if high-power.
Close up the enclosure, attach connectors, and do final validation tests. Your professionally mounted circuit board is complete! Power up and enjoy your creation.
Pro Tips for Mounting Boards
Here are some expert recommendations for flawlessly mounting PCBs:
Use plastic standoffs – Nylon or polycarbonate standoffs insulate the board from the enclosure versus metallic types. This helps prevent stray Ground paths or short circuits through chassis contacts.
Avoid torque twisting – Uneven tightening of mounting screws can warp the board which strains solder joints. Tighten opposing corner screws gradually to maintain even pressure.
Mount sensibly sized boards – Overly large boards can flex and crack under their own weight without proper support. Use mounting holes evenly spaced across the PCB or structural reinforcement.
Allow ventilation space – Leave clearance between high power boards and enclosure walls for airflow convection cooling. This prevents overheating damage.
Conformal coat when necessary – For boards in harsh environments, apply acrylic coating to shield against moisture corrosion or dust contamination.
Use mounting templates – For production assemblies, laser cut acrylic templates allow consistent hole alignment when positioning boards prior to screwing down.
Paying attention to these professional tips will help your mounted boards function reliably for years of service.
Common Mounting Methods
There are several standard techniques for securing a PCB depending on the intended application:
| Method | Description |
|---|---|
| Standoffs | Separate cylindrical supports that screw into case |
| Risers | Card-edge connectors allow stacking multiple boards |
| Rack slides | For larger chassis with shelf-like card guides |
| Adhesive pads | Double-sided foam tape bonds board temporarily |
| Edge clips | Metal brackets that grip the board perimeter |
| Angled slots | Oblique case cuts support PCB edges |
| Face plates | Panel-mounted IO ports hold board from front side |
Selecting Proper Standoff Type
Choosing ideal standoffs is key for robust yet simple mounting. Variables that influence the selection:
| Consideration | Options |
|---|---|
| Board thickness | 1-6 mm standoff lengths available |
| Board height | Standoffs from 1/4 to 2+ inches tall |
| Number of boards | Single or multi-stacking standoff types |
| Material | Nylon, brass, aluminum, stainless steel |
| Screw type | Matching threads for case material |
| Hex or Phillips drive | Drive style for accessing screw heads |
Nylon and brass are common cost-effective options suitable for most applications.
Troubleshooting Mounting Problems
Despite best efforts, you may encounter issues getting a board securely mounted such as:
| Problem | Likely Causes | Solutions |
|---|---|---|
| Board doesn’t align with standoffs | Enclosure tolerance variation | Use slotted holes, shims, extra washers |
| Board loose with play | Loose screws, stripped threads | Use next screw size up, add washers |
| Components make contact | Tall parts touch cover | Raise standoffs, double check layout |
| Unable to access component side | Close proximity to chassis | Use only low-profile nuts, risers |
| Circuit fails intermittently | Thermal cycling moves board | Conformal coating, vibration damping |
Careful inspection of the actual assembly and planning ahead for mechanical clearance helps mitigate problems. Having standard troubleshooting steps in mind allows you to methodically isolate and remedy mounting-related issues so your board operates reliably.
Mounting Boards in Practice
Here are some examples of mounted boards seen in real electronic products:
| Application | Mounting Method |
|---|---|
| Desktop PCs | Vertical riser cards and large cross braces |
| Set-top cable boxes | Small standoffs epoxied directly to plastic enclosure |
| Rackmount servers | Shelf-like horizontal card guides with injection levers |
| Network switches | Faraday-cage aluminum cases, edge tab mounts |
| Handheld devices | Miniature boards fixed in place with globs of silicone |
Mass-manufactured products utilize optimized, automated mounting techniques tailored closely to the particular board, case, and operating environment. But small-scale projects can achieve similar robust results with mindful part choices and manual installation precision.
Mounting Factors
What determines how a printed circuit board gets mounted?
- Vibration/shock – Will product move around?
- Thermal – Does circuit dissipate much heat?
- EMI/RFI – Plastic standoffs or metal cage?
- Access – Need to remove easily?
- Volume – Manual or automated process?
- Aesthetics – Visible or hidden board?
Analyzing key aspects like these helps dictate ideal mounting methods per application.
FAQ
What are some main advantages of standoffs?
Standoffs securely space boards off conductive enclosure surfaces. They dissipate heat better, allow washers for uniform screw pressure, permit component clearance, and simplify wiring access underneath. Standoffs are affordable and don’t require special tools.
What screw size should I use?
Match screw diameters to mounting hole sizes, allowing 0.5 mm extra clearance. Standard hole sizes are 2.5 mm, 3 mm, and 3.5 mm in most PCBs. Screw lengths depends on stacked board height plus 20-50% extra for safety. Too long and screws bottom out. Too short and threads don’t catch.
Is epoxy a durable mounting method?
Structural epoxies bond well but allow little shear strength, flexibility against vibration, or heat transfer for cooling. Epoxies work only with very lightweight boards. Use reinforced epoxy gel for increased strength. But fasteners permit easier component access and board removal.
What are clearance requirements around boards?
Leave at least 3 mm spacing from enclosure walls and tall components to allow some air circulation. High power circuits require greater clearance or fans. Carefully measure height of tallest elements like capacitors to ensure sufficient headroom when the lid closes.
How can I prevent loose screw connections?
Use threadlocker adhesive so screws resist backing out over time. Split lock washers also fight loosening but add height. When screws won’t grab sufficiently even with washers, replace the standoffs or case threaded holes with next larger size up.
Conclusion
Mounting a printed circuit board properly involves planning enclosure integration details plus allowing maintenance access and expansion capacity. Carefully installing standoffs or other mechanical supports ensures the board remains fixed securely during shipping or operation. Troubleshooting both solder connections and physical mounting integrity prevents erratic failures.
With mindful material selection and methodical fastening techniques, you can achieve dependable mounting of your custom circuit board for years of reliable functionality.
