Printed circuit boards are valuable commodities, used for a variety of different purposes in this day and age. The revenue of PCBs in 2014 alone was around $44 billion. The industry itself was valued at $7.1 billion in 1995, just 50 years after it started — and by 2000, it was worth $10 billion, rising to $60 billion worldwide in 2012. The demand for PCBs often requires mass production, as they’re often ordered in batches. Even low volume PCB assembly can require the production of dozens of PCBs. While PCBs were once made by hand, machine assembly has become favored in more recent years. This has led to the concern that there could be a drop in quality — while in fact, PCBs made in machine assembly lines are usually of the same quality as handmade PCBs, and are made more efficiently. However, PCB inspection remains an important part of PCB assembly services. Below, we’ll look into what the PCB assembly process, as well as what is expected of PCB inspections.
Machine-Made Versus Handmade PCBs: The Difference
Unfortunately, there remains a perception among the general populace that machine-made products are not as high-quality as handmade products. When it comes to PCBs, this is just not the case. Prior to the introduction of PCB design software, printed circuit boards were usually designed using clear, Mylar sheets. They were up to four times bigger than the circuit boards themselves, and designers had to create a clear, transparent photomask of the desired design. This understandably took a lot of time, and did not eliminate the need for PCB inspection. It was difficult for even small batch orders to be fulfilled in a timely manner. After machine assembly for any size order was invented, shops could assemble PCBs in a fraction of the time it took by hand. As it is, some PCB assemblers have a standard turn-time of five days or less. This is 75% faster than the industry average. Furthermore, a single automatic line can place and solder more components than 50 hand solder operators — and they do it with better, more consistent quality. Machine assembly doesn’t mean that engineers become obsolete, rather that they can focus on other details, rather than solely working on assembling PCBs.
PCB Inspection: What Is Required
Certain consistencies are required of all PCBs. For example, the spaces between electrical conducting paths often have to be .04 inches or smaller, and board designers use special, computer-aided software to make these spaces. Conversely, PCB trace thickness is measured in ounces of copper. Most often, PCB designers use one or two ounce of copper thickness, but many PCB manufacturers can provide up to six ounce of copper thickness. This too will be measured during PCB inspection.
Quality Control: When There Are Problems
Though PCB quality control issues may not be common, you’ll want to know why they happen, understandably. Usually, 70% of all surface assembly quality issues can be accounted for by printing technique. The other problems can often be accounted for by PCB design, the quality of the components, and the quality of the printed boards themselves.
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