PCB Technical - Precautions for starting PCB prototype?

Things to check before starting the PCB prototype

A single carelessness may turn all your efforts into a huge waste of time and money. Printed circuit boards need special attention in production services, so you need to be careful about PCB design before entering PCB manufacturing, PCB assembly and assembly services, and PCB manufacturing. Before you boot your prototype, pay attention to these anomalies:

1. Short circuit

Short circuit is one of the most important reasons for PCB prototype damage. You need to pay attention to fine-pitch components, such as microcontrollers with LQFP footprints. Tiny solder leads that cause a short circuit between two adjacent pins may permanently damage the microcontroller during power up.

It is always a good idea to measure the impedance of each type of voltage node with respect to ground. For example, you may have 12V, 5V, and 3V power supply networks in the PCB, and any of them may be shorted to ground through incorrect soldering or faulty components. This may cause the affected components to heat up sharply when energized.

What are the precautions before starting the PCB prototype?

Short circuits are the culprit behind most damaged prototypes.

2. Reverse polarity

If you turn on the power with some logic integrated circuit (IC) soldered in the opposite polarity, you won't look back. You will see a quiet bang, a cloud of smoke and a familiar pungent smell. If you are lucky, it will be easy to remove the damaged parts. Otherwise, you may need to deal with damaged pads.

In manual assembly, there is bound to be a risk of human error. Even if you are willing to increase the cost to obtain a small number of prototypes completed by the machine, manual placement of board-to-wire connectors can sometimes be wrong. Always make sure that each component is assembled according to its polarity.

3. Filling components

It can be frustrating to spend several hours to rule out the reason why the microcontroller cannot start, just to realize that the load capacitance of the crystal oscillator is not filled. When you assemble hundreds of components on a new design, you may miss one or two components.

When a PCB factory uses PCB prototyping or PCB prototyping services, you need to ensure that the production can use the components you want to make the circuit board you intend to make. Before you start cross-checking each component, make sure you have the latest bill of materials (BOM) list.

Precautions to be taken before opening the PCB prototype

Even if you think you may have covered all the foundations, when you turn on the power switch, there may be problems. This is why it is a good idea for PCB manufacturers to add some LED indicators representing different voltage levels on the PCB. If the corresponding voltage regulator is turned on when power is applied, it will immediately sound an alarm.

The measured voltage level is 100% confirmed.

Even if the LED is lit, you need to measure the voltage of each regulator to confirm whether their value is appropriate. Sometimes, a partial failure of certain components may significantly reduce the voltage level, but keep the indicator LED on.

If one or more LED indicators are not turned on, please cut off the power immediately. PCB prototype. This is usually a sign of component damage. Or, you may forget to solder certain components. If it is the former, you may notice that a certain part of the PCB will heat up abnormally in a short period of time.

But in the case of missing components, cross-referencing the BOM will help you find the missing parts. PCB assembly services through printed circuit boards need to consider the circuit board. To ensure that you always have the latest BOM, you need intuitive PCB design software (such as AltiumDesigner®) to automatically generate the BOM.