Test SMT Components Before Placing

Simple components like resistors capacitors and diodes are quite common on surface mount printed circuit board assemblies. At PCBbee we buy hundreds of thousands of reels a year, usually from major distributors. Several times a year, we get a reel that is mislabeled. The value of the component is not what the label says it is. Sometimes it is the manufacturer’s error, sometimes it is the distributors. At some contract manufacturers, entering the wrong part number in receiving is a common mistake. Here we’ve eliminated that potential source of error by scanning incoming parts rather than doing manual data entry.

Once a component with the wrong value is placed on a board, it is very hard to detect it and can cause some very expensive problems. The small smt packages that we use most often are not individually marked and so a one nano farad capacitor looks exactly like a 10 nano farad capacitor. Automated optical inspection won’t catch it. In-circuit testing may catch it perhaps half the time, but it is more likely to remain undetected until it causes problems, such as high emi because the decoupling capacitor has the wrong value or rapid battery drain because the current draw is higher than we expected due to a wrong value pull-up resistor.

At PCBbee, we think the best solution is to verify the value of these components before we place them. There are a couple ways to do this. One is that we’ve enable an advanced option on our micronic pick and place machines to test the first few components on a reel whenever a new reel is loaded. This option checks resistors and capacitors for the correct value, it also checks diodes for the correct polarity.

Testing components before we place them is just one more way that PCBbee maintains high quality and keeps down our costs for our contract manufacturing customers. Contact us at service@pcbbee.com to learn more about pcb assembly in China.