Checklist for Systematically Testing PCB Prototypes
During my teenage years, I spent fifteen whole minutes perfecting my hairstyle before walking out of the house. Looking back, I’m pretty sure the mirror was tired of my vanity. These days, I walk to work without putting a single drop of gel on my hair. My unkempt appearance sometimes amuses strangers but my close friends know that I’m just being myself.
Although I no longer obsess over my physical appearance, my perfectionist attitude comes into play as I’m developing electronics prototypes, especially before powering up the first assembled unit. After spending hours placing hundreds of components on the PCB, the last thing I want to do is to literally blow it up. In this case, perfectionism is crucial. If you have a bad reputation for damaging PCB prototypes because you overlook certain details, check out the following tips to ensure your PCB is fully ready to be powered up.
Things to Inspect Before Powering Up Your PCB Prototype
A single moment of carelessness can turn all of your efforts into a colossal waste of time and funding. Printed circuit boards are particularly necessary to pay attention to during production services, and so before moving into PCB fabrication, PCB assembly and assembly services, and PCB manufacturing, you’ll want to be careful with your PCB design.So before you even power up your prototype, look out for these anomalies:
1. Short Circuits
Short circuits are one of the most reasons for damaged PCB prototypes. You need to pay attention to fine-pitch components like a microcontroller with an LQFP footprint. A tiny solder lead that causes a short between two adjacent pins can permanently damage the microcontroller when powered up.
It’s always a good idea to measure the impedance of every type of voltage node with respect to the ground. For instance, you may have 12V, 5V and 3V power network in a PCB and any of them may be shorted to ground, either by improper soldering or faulty components. This could cause the affected component to heat up drastically when powered up.
Short circuits are the main culprit behind most damaged prototypes.
2. Inverted Polarity
If you’ve flipped on the power with some logic integrated circuits (IC) soldered in the opposite polarity, there’s no going back. You’ll be greeted with a quiet popping sound, a tiny cloud of smoke, and the familiar acrid scent. If you’re lucky, removing the damaged components will be easy. Otherwise, you may need to deal with damaged pads.
When it comes to manual assembly, there is bound to be a risk of human error. Even when you are willing to increase your expenses to get a handful of prototypes completed by a machine, manual placement of board-to-wire connectors can sometimes go wrong. Always ensure that every single component is assembled according to its polarity.
3. Populated Components
It can be frustrating to spend hours troubleshooting why the microcontroller fails to start up, only to realize that the load capacitor of the crystal oscillator was not populated. When you’re assembling hundreds of components on a new design, there is a chance you may have missed a part or two.
When working with PCB prototyping or a PCB prototype service, you’ll need to ensure production is capable of crafting the circuit board you intend to make with the components you want. Before you start cross-checking every single component, ensure that you’re holding on to the latest bill of materials (BOM) list.
Precautions to Take Before Powering Up a PCB Prototype
Even if you think you may have covered all bases, there are chances that things would go wrong the moment you hit the power-up switch. This is why adding a few LED indicators that represent the various voltage level on the PCB is a great idea. It alerts you immediately if the respective voltage regulator is turned on when powered up.
Measure the voltage level to be 100% sure.
Even if the LEDs are lit on, you’ll need to measure the voltage for each voltage regulator to confirm they are at the right value. Sometimes, a partial breakdown of some components may significantly pull down the voltage level but leave the indicative LED turned on.
In the case where one or more LED indicators are not turned on, immediately cut off the power to the PCB prototype. This is often a sign of a damaged component. Alternatively, you may have forgotten to solder some components. If it’s the former, you may notice that a certain part of the PCB heats up abnormally within a short time period.
But if it’s a case of a missing component, cross-referencing with the BOM will help you identify the missing part. Working through your printed circuit boards toward PCB assembly services will require a consideration for your circuit board. To ensure that you always have the latest BOM, you need intuitive PCB design software like Altium Designer® to automate BOM generation.
Need more tips in safely testing your PCB prototype? Talk to an Altium expert today.