Custom Electronic Enclosures: PCBA Protection and Performance

Manufacturing electronic devices is a painstaking task that requires extreme levels of process control to prevent contamination that sullies quality and threatens performance. However, a device still needs to protect against the ingress of contaminants throughout its service life. Since the function of electronics can vary wildly, so too can the enclosures that house them.

Form factors have become a pervasive design consideration with a greater emphasis on lightweight and portable devices, which has a pronounced effect on printed circuits and their enclosures. At VSE, we’ve been engineering PCB solutions for over 40 years, and your custom electronic enclosure design contains as much dedication and rigor as the boards residing inside.

Enclosure Attributes

Mechanical

Weight
Shock/impact resistance (portable)
Vibration – bolting may be necessary for large equipment
Accessibility

Thermal

Surface area/volume
Passive/active cooling
Placement of active cooling elements within the enclosure
Heating (for cold outdoor usage)
Humidity control (prevent corrosion)

Materials

Heat transfer coefficient
Brittleness/ductility
Weight
High temperature/corrosive environment suitability
Dust-tight/air-tight (submersible)

Keeping It Cool with Custom Electronic Enclosures

The inherent difficulty of enclosures and electronics is thermal management. While enclosures benefit electronics overall, they can impede thermal dissipation by impeding airflow around and away from the board. This problem can become magnified with multiple devices stored in a single rack-style enclosure.

Proper enclosure design maximizes the cooling potential of passive and forced airflow to ensure devices’ temperatures remain within normal operating conditions, maintaining performance and extending service life. Sensitive electronics enclosed in outdoor environments subject to freezing temperatures may have to contend with heating and cooling throughout the seasons to keep electronic devices functioning and depress the relative humidity.

Enclosures must regulate the temperature rise from device heat dissipation but may also have to contend with significant external heating in specific industrial settings. Heat dissipation always occurs in a high-to-low direction, and higher ambient temperatures will require more effective cooling to keep devices within an acceptable temperature range.

Thermal management strategies vary depending on the temperatures involved, the heat power dissipated by the device, and the enclosure’s level of openness to the environment:

Passive cooling

Where ambient temperature outside the enclosure is lower than inside, radiative and convective cooling will occur. Generally, this cooling method is insufficient for most devices, but possible exceptions include very low-power devices and devices where enclosure size and form are less constrained. A relatively cool environment free from particulate can place louver vents at the top of enclosures and drive air with a low-speed fan toward the bottom.

Forced convection

Air is mechanically forced into the enclosure by a filter fan. Since more air passes through than passive cooling, there is more opportunity to sink heat. This method still requires a meaningful temperature difference between the interior and exterior of the enclosure. The filter fan can be supplemented with internal fans if there are concerns about hot spots forming that are less susceptible to system convection cooling alone.

Enclosure cooling

If particulate or other environmental factors are a concern, enclosure design can effectively separate the ambient air from the internal air used for cooling. These closed-loop systems rely on robust refrigeration systems like heat exchangers and air conditioners, which comes at a greater cost than other listed cooling methods. Air conditioning has the advantage that it can still provide cooling even when the ambient temperatures match or exceed the internal temperatures. Thermoelectric coolers can also operate without a temperature gradient and can be beneficial in enclosure settings that lack the space for A/C.

Calculating the cooling capacity will depend on the cooling method, but most rely on the temperature differential between the enclosure and ambient air, the power generated, the heat coefficient of the material, and the exposed surface area. Rough calculations made while deciding upon enclosure design will give way to sophisticated thermal models.

Iterating on Common Enclosure Styles

Preventing the ingress of moisture and other matter is the primary function of the enclosure. Depending on the electronics and the operating environment, either may be nonfactors or pose a critical interruption to service reliability. The enclosure style will also play a significant role in its suitability for a specific electrical or electromechanical application:

Pushbutton – This format adds pre-cut openings for mechanisms like buttons, switches, and indicators to various enclosure configurations.
Floor-mounted/freestanding – Many electronic devices will want to remain floor-mounted due to weight/vibrational action. Floor-mounted enclosures provide excellent stability, with securing/bolting offering further enhancement.
Pushbutton – This format adds pre-cut openings for mechanisms like buttons, switches, and indicators to various enclosure configurations.
Consoles – Consoles house electronic controls and instrumentation in an enclosure that is readily accessible for system operation. They tend to have a more heavy-duty construction due to their role and consistent usage.
Wire-through – These enclosures protect wiring from surrounding equipment and the environment.
Sloped top – An enclosure variant that features a gently sloped top and door flanges to prevent the buildup of dust or water. Sloped tops are most useful for installations in harsh or dirty environments where debris accumulation is consistent enough to require frequent washdowns.
Windowed – A see-through panel allows viewing inside the enclosure without exposing the inside to debris or moisture.
Dual access – Some deeper enclosures may arrange devices consecutively in lines or rows. Accessing devices in the back can be tricky; dual access doors allow the enclosure to open from the front or rear.
Flush mount – Areas with significant space constraints can opt for a recessed enclosure that leaves the access door flush with the wall.

Your Contract Manufacturer Has All Aspects of PCBA Covered

At VSE, custom electronic enclosures are just one of the box-build elements we supply for our customers. Whatever design stage your product-to-be is at, our engineering team is ready to lend their expertise to improve performance, manufacturability, and lifetime reliability.

We can add wire harness and cable assembly capabilities for devices at the prototype stage to expedite testing and create durable connectivity that stands the test of time. We also offer a seamless manufacturing transition to our high-volume production facility located in Reno, NV, with the same equipment and design oversight our customers have come to expect over the past 40 years in San Jose.

If you are looking for a CM that prides itself on its care and attention to detail to ensure that each PCB assembly is built to the highest standards, look no further than VSE. Contact us today to learn more about partnering with us for your next project.