I’m usually courageous. But when I realized I broke the porcelain bowl prized by my other half, I broke out in cold sweats. After surviving the nagging and making promise after promise of replacing her favorite culinary item, I sighed in relief. I vow to be more attentive when handling fragile items at home.
At work, I ensure such mistakes do not happen with the PCB that has been assembled. With hundreds of miniature components soldered, a PCB is less robust than you imagined. When not handled correctly, you may be receiving a stream of complaints from unhappy system installers as the circuit may fail to function correctly.
Should PCB Designers Care About PCB Handling?
Chances are, you may not lay a finger on the hundreds of PCBs manufactured from your design. It is the assembler, test engineer, installers, and maintenance personnel who will be in contact with those PCBs.
The fact that you will not be involved in the post-production process doesn’t mean you can be complacent about PCB handling. It’s important to be informed about the proper PCB handling process and how failing to do so may result in malfunction circuits.
What’s more important is that PCB designers should be aware of their role in optimizing the PCB layout so that issues pertaining to PCB handling can be reduced. The last thing you want is to rework an existing PCB when you should have been challenging yourself with the next project.
How Improper PCB Handling Could Cause Damage
Given a choice, I would rather deal with broken porcelain than problems caused by improper PCB handling. While the former is blatantly obvious, damages caused by PCB handling issues are more subtle. Often there are no obvious signs until the PCB fails to function when deployed.
A common problem observed when a PCB is not handled with care is active components fail due to the electrostatic discharge (ESD) from the individual. This happens when PCBs are handled in a non-ESD safe environment. For ESD-sensitive components, it takes less than 3,000 volts to cause real damage to its internal circuitry.
If you take a closer look at a reflow-soldered PCB, you’ll notice that only a tiny amount of solder is holding the surface mount (SMD) components to the pad. Components such as SMD capacitors can have one of their pads disconnected when mechanical force is applied in parallel to the PCB.
In other words, when you attempt to pick up a PCB with a single hand, you’ll be pressing the PCB against itself. This may cause the PCB to bend slightly and may dislodge some components from its pads. To prevent this, it is a good practice to pick up a PCB with both hands.
Improper PCB handling may cause electronics to malfunction.
PCBs are often panelized to reduce cost and improve efficiency. After they are assembled, you’ll need to break the PCB apart. Even though they are held by minimal V-scored support, you’ll still need to apply some force to break them apart. This process may also accidentally damage the solder point of some components.
While it’s not common, sometimes carelessness gets in the way, and you drop a PCB on the ground just like I did with the porcelain bowl. The sudden impact can damage larger components like electrolytic capacitors and even tear of the pads from the PCB.
Design Techniques To Reduce PCB Handling Issues
PCB designers aren’t totally helpless when it comes to dealing with PCB handling issues. To a certain extent, implementing the right design strategies help in minimizing defects associated with PCB handling.
To prevent sensitive components from failing due to ESD, you’ll want to add protective components that suppress the transient during the static discharge. Varistors and Zener diodes are usually used to deal with the quick discharge of ESD. Besides, there are dedicated ESD protection devices that offer better protection for such phenomenons.
ESD protection is essential when handling PCB.
You can’t prevent PCBs from being exposed to mechanical stress. However, you can mitigate such problems by ensuring the components are placed in a certain manner. For example, you knew that placing SMD capacitors in line with the breaking force applied in depanelizing increases the risk of the solder breaking apart.
Therefore, you’ll want to arrange the SMD capacitors or similar parts in parallel to the break-line to minimize the impact of the force applied. Also, avoid placing components near to curvature or bend lines of a PCB, as well as avoiding placing components close to the board outline.
Of course, it helps to have OrCAD PCB design software that allows you to visualize the design in 3D, as it will enable you to address any mechanical constraint that may affect PCB handling. The 3D ECAD feature of Cadence PCB layout software is a fine tool in that respect.
If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts.