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Eight PCB Assembly Tips for 2019

It's now 2019, and all I'll say on the coming year is that we are in for a wild ride. The last few years have been pretty crazy, and 2019 looks to continue that trend but amped up. Don't worry though. If it seems like things are at their worst, they aren't. It's just the cycle.

Despite anticipation of a roller coaster of a year, I'm still quite optimistic. The most long-term successful aspects of our civilization are those that rip apart on a regular basis. Frequent disruption allows people to start new and create bigger and better things. Without that, we end up focusing too much on holding on to what already exists. Innovation stops, and decay and despotism take hold.

The United States isn't all that different from the rest of the world, but I'm reasonably convinced that one of the main things that sets us apart is that we are constantly on the verge of self-destruction. This breaks up entropy and creates a breeding ground for innovation. It's an endless cycle of shredding and reinventing, and that reinventing makes progress possible.

While predictions might be fun to muse upon, they really won't help you get your job done. However, my top eight pieces of PCB assembly advice for the coming year should make up for that.

1. Before you even start component selection, give thought to the design scale.

What's more important—board size, cost, or time to layout? A large board will be easier to route but will cost more for the fabricator. A smaller board will cost less for the fabricator in terms of square inches but may cost more due to extra layers or take longer to layout.

2. Factor in the cost of component size.

For passives, roughly 0603 size parts will probably be the sweet spot in terms of lowest cost. The 0603 is also a good size for overall handling. We'll assembly down to 0201 parts, but not all manufacturers will. Also, 0603s are easy to rework and manageable if you feel the need to hand solder a few.

3. Check out any exotic or new parts.

These days, some parts are only available in super small wafer-scale BGA or QFN form factors. Take a look at your integrated circuits and make sure they come in packages that you're comfortable working with.

4. Check for sole-source or low-availability parts.

The last thing you want is a completed design that's sitting around waiting for one sole-sourced part with a long lead time. If a sole-sourced part is at risk for availability, you might want to find something similar and more available.

5. Don't forget manufacturing thermal concerns when laying out your board.

Very large parts next to very small parts can cause problems. The large parts will act a bit like a heat sink and may prevent the solder for the small part from melting properly. The same thing can happen with internal copper planes that overlap on half of a small part but not the other.

6. Give extra care to the clarity of reference designators and polarity markings.

Make sure that it's very clear which designator goes with which part, and that there isn't any ambiguity in polarity markings. Take special care with LEDs because manufacturers sometimes swap polarity markings between the anode and cathode; yes, the exact same mark can mean anode on one LED and cathode on another. Also, do your best to keep reference designators off of vias or any other spots that might break up the text.

7. When you're ready to send your project to be built, give your files a double check.

Make sure you have the correct versions. Bills of materials are especially susceptible to having bits of information out of date that might cause delays.

8. If you're sending in a parts kit, double check that you have all of the parts.

Ensure you have the part number and reference designator on the individual part bags.

Paying attention to component shortages is crucial. Every few years in the electronics industry, the dreaded word “allocation” rears its head. It’s doing it again, but with even more gusto than usual. As a manufacturer, components are pretty important. We can’t build anything without them, so we pay close attention. Our components suppliers are telling us that this is the most extreme shortage period in recent memory. We’re told that this is spearheaded by automobile electronics and IoT devices.

Not only are components difficult to find but we’re also being told that the way they are built is going to change. Larger package sizes may go away and never come back. We can’t make these component shortages go away in the manufacturing world, but by working together, engineers and assemblers can keep the disruption to a minimum. We want nothing more than to see working boards in your hands when you need them. Manufacturing is just putting parts on boards, but it's doing so with a whole lot of variables. A few extra checklist steps can go a long way toward removing the variability of those variables.

I wish I knew what the solution will be in 2019—that would be a great business to go into—but it's way beyond me. Someone will figure this out within the next decade, and when they do, a lot of unrealized potential will suddenly open up.

Duane Benson is chief technology champion at Screaming Circuits. To read past columns or contact Benson, click here.