What is a PCB board?

printed cicuit board
A PCB board is a thin board that is made of fiberglass, some kind of epoxy that hardens over time, or another type of laminate material.

PCBs are used in any type of standard computer or laptop computer. PCB boards are the heart of the computer. When Steve Jobs, founder and CEO of Apple, the most famous and wealthy tech company today, first developed his PCB design, he made a deal with a local computer store for the boards whom he had impressed at the “Hometown Brew Club,” a small computer startup club that was popular during the early days in the Silicon Valley area.

You Mean There’s More to It Than This?

The deal he made was for the boards alone, so Jobs took his 10 boards to the computer store, thinking that the board alone was all he wanted. He was mistaken. The man wanted entire computer systems! He argued, “These are killer boards!” He took for granted that consumers understood the process that went into the building of the board and that they would be willing to learn how to put the parts together.

Back to the Drawing Board

circuit board Needless to say, they had to go back to the drawing board and add all of the peripherals including keyboards, monitors, and other attachments. But before Jobs left his store, he got him to agree to buy 50 rather than 10.

He quickly hired as many engineers and people who could fit in his garage and started to work. A few weeks later and under deadline, Jobs appeared with the completed systems and collected their first big paycheck!

These guys were determined to get this deal through and they worked day and night without stopping to meet their deadline.

What about Today?

In the real world today, you can’t time this kind of time out of your business to put together 50 units in just a couple of weeks. Even if you work well under pressure, you are going to find it difficult to crank out this many units in the amount of time you need to without disrupting the everyday processes of your business.

If you are a manufacturer, this is what you do every day so it may not put you at a disadvantage. But what about ramping up? As you increase your output due to customer or market demands, you may find it difficult to keep up with the demand.

PCB Assembly

pcb assemblyThe Surface Mount Technology (SMT) is an automatic mounting process used in PCB assembly to attach components to the PCB’s surface. SMT makes it possible to make highly-complex electronic circuitry into small-sized assemblies with good duplication due to its high- level automation capability. The SMT process begins with placing the solder paste onto the board and ends with reflow soldering.

  1. The first step (solder-paste-printing) involves using a solder paste printer to apply the paste on a plain board. A solder screen or stencil is then used to ensure that the solder paste is placed appropriately where the components are supposed to be mounted. The quality of a solder printing depends on the quality of the soldering done. For a successful PCB assembly, an inspection is conducted using a solder-paste inspection machine after the solder-printing process. This inspection ensures the solder-printing meets standards and regulations. If there are any defects found, the printing process must be done again.
  2. The second step (components mounting) involves placing electronic components on their corresponding pads or contact points using an SMT machine. The machine picks and places the components through reels rotating to provide the components to the SMT machine, which sticks them to the printed board with the solder paste.
  3. The final step (reflow soldering) is to firmly bind the mounted components to the board by liquefying the solder paste and passing it through a furnace with a temperature of 500°F.

How Are PCBs Tested?

There are two main ways to test out a PCB: with flying probe tests and with universal grid testing. Both tests look for the same things – opens, shorts, resistance and capacitance – but how they test for them differs.

A flying probe test uses mobile sensors to examine the components on each printed circuit assembly. With the help of a two-axis system, they examine the board from top to bottom, while their probes test contacts and test points. The upside of this type is that it doesn’t require its own extra machine.

A universal grid test is done with its own machine is often seen as more accurate than a flying probe test. This is because a universal grid test uses two high resolution cameras, positioned at the top and bottom of the board, to scan the board. This allows tested to make minor adjustments if needed.