How Ultrafast UV Lasers are Improving HDI PCB Design Layouts

Do you remember the first time you saw Star Wars? I was 12 and it changed my world forever. I’d seen my future. Instead of a car, I would fly a spaceship. Instead of being an accountant like my father, I would be a lightsaber-wielding Jedi. Sadly, I turned out to be neither a Jedi or an accountant, but a humble PCB.

Lasers still have a place in my life, though not in the way I thought they would. Instead of using them to blast holes in the Death Star, I let manufacturers laser drill microvias in my high density interconnect PCBs. So I guess I’m more like the Emperor than Luke. My laser zapped PCBs are improving as a result of advances in ultrafast UV lasers. These let manufacturers pepper my boards with smaller vias more quickly. Shrinking vias will mean more dense PCBs, with less EMI and potentially lower manufacturing costs.

Advances in Lasers

As time passes standards change. I wanted to marry a girl with hair like a pair of honey buns, but I settled for one that likes to eat honey buns. Like side hair buns faded out “long, long ago”, CO2  lasers are becoming a thing of the past. Ultrafast UV lasers enable manufacturers to further shrink via sizes. What’s more, these tiny vias can be drilled faster than the current industry standard rate with little or no thermal issues.

When CO2 lasers were, the bottom diameter of microvias was around 60-80 µm. New ultrafast UV takes the lower limit down to 15 µm. Not only do ultrafast UV lasers drill small vias, they also drill them...ultra fast. These researchers were drilling vias at 2,800 holes per second, which is 800 faster than the industry standard of 2,000 holes per second. You may not be too worried about fabrication time, but faster production will translate into lower costs for you.

Part of the reason these vias can be drilled faster is because it takes less power to drill them. Lower power leads to another advantage, less heat. Ultrafast UV lasers can drill microvias with practically no heat affected zone (HAZ).

Maybe this all sounds like Ewokese to you, what does it all mean? Smaller, faster, cooler laser drilling methods will allow you to shrink your traditional and flexible boards. In addition, they’ll help you reduce EMI on your boards.

Higher Density Traditional Boards

Narrow diameter vias automatically translate into smaller boards. Tiny vias leave more space for other components, like heatsinks. Make those little vias buried or blind to save even more real estate. Lasers can be used for more than vias, though. You may need to cut channels or gaps in your power or ground planes to reduce EMI. You don’t want it to look like a Stormtrooper randomly blasted those holes in there. UV lasers can make those cuts smaller, with a higher accuracy than other methods.

Tiny vias are a great technology that allow you to use other great technologies. Package pitches are shrinking. Traditional vias just won’t do it for that new ball grid array (BGA). Narrow vias are perfect for the via-in-pads (VIPs) that help you break out fine pitch BGAs. Speaking of breakout, smaller vias make for a much more efficient breakout, which can really help reduce the size of your board.

Higher Density Flexible Boards

Size is even more important in rigid flex and fully flexible designs. Whether you’re designing flexible boards for the Internet of Things (IoT) or automotive applications, space is tight. You don’t want your board installation to be like trying to cram Jabba the Hutt into a TIE Fighter. Ultrafast UV lasers will help you design smaller boards that cost less to fabricate.

Cuts and channels are often used for EMI purposes on traditional boards. On flexible boards’, a necessity required in order to meet space demands. Again, you need a manufacturing process that has the agility of Yoda, not the brute force of Darth Vader. The accuracy and small focal point of ultrafast UV lasers will enable you to shrink the cuts and channels on your flexible board.

You’re probably thinking, okay, this is all fine in theory, but ultrafast drilling must be ultra expensive right? Wrong. Even if your accountants are like the Sith, they’ll absolutely love the price of ultrafast UV drilling. Most flexible boards use a combination of materials that must be laser cut at the same time to reduce cost. It just so happens that ultrafast UV lasers are the perfect tool for the job. Using one tool for all cuts and holes means your manufacturer will save money on fabrication. You’ll just have to hope that they pass the savings onto you.

The mounting materials used for flexible boards can also be a problem if the manufacturing method is too hot. Occasionally, flexible boards are mounted on paper for drilling. If the laser doing the drilling is too hot, your board might go up in smoke. Remember that ultrafast UV lasers transfer minimal heat to your board during fabrication. This makes them the perfect weapon for cutting/drilling your Death Star shaped PCB.

CO2 lasers have failed us for the last time. Editorial credit: Stefano Buttafoco / Shutterstock.com

EMI Reduction

I like to talk about EMI as much as Obi-Wan likes to talk about the Force. They’re both invisible and mysterious, so maybe they’re the same thing. I could really be a Jedi Master. Anyway, smaller vias will reduce EMI on your boards.

Vias are basically antenna, they radiate EMI. Via stubs can also cause signal reflection and degrade signal integrity in your high speed boards. The smaller the via, the less it will radiate EMI. When you reduce a via’s size, you reduce its impedance as well. Lower impedance leads to less voltage drop. It seems like the FCC sometimes has the senses of Yoda. They can feel the force of EMI, which most people wouldn’t notice. Using the narrowest vias possible will keep them from making dumb jokes like, “the EMI is strong with this board.”

Well, I tried to make as many Star Wars jokes as possible, but the advantages of ultrafast UV lasers are no joke. They’ll allow your manufacturers to shrink your vias, make your boards faster, and possibly reduce your costs. Tinier vias lead to higher density boards, both flexible and traditional. Additionally, narrow vias will help reduce EMI on all kinds of PCBs.

Ok ok, one more star wars joke. Obi-Wan told Luke to “use the Force” in lieu of his targeting computer. Well, you’re not Luke, so I suggest you use a computer for your designs. PCB design software may not be able to shoot lasers, but it can help you utilize the advantages of lasers. CircuitStudio^® is a cutting edge program that can help you leverage the full potential of ultrafast UV lasers.

Have more questions about lasers? Call an expert at Altium.