Laser Drilling Services for Precision Drilled Panels
Looking at a modern printed circuit board you may get dizzy trying to wrap your head around the design and intricate, complex relations between the components on the board. Even the most seasoned electrical engineers won’t be able to decipher the code that easily without some hints.
Though the final board designs are intimidatingly complex, the design process itself is far from it. Design engineers usually follow the simple concept of divide and conquer. One way to look at it is to think of major electronic components (integrated circuits) on any board as if they are buildings. In real life every building has to have certain “utility” systems around it to make sure that the building is doing its function correctly, systems like gas, electrical and water for example. In electronic design, each IC needs certain passive components like resistors and capacitors arranged around it to enable it to do its job.
Once you have every IC (building) set up and ready to do its thing, you still need a way by which each of these ICs communicates with the rest of the ICs on the board to fully perform the board’s designated function.
Much like actual cities where streets and roads connect buildings together, ICs on a board are connected to each other with copper traces. And just like any metropolitan city, urban expansion tends to move vertically instead of horizontally, but instead of multi-story buildings, we get multilayer boards.
To keep all the components connected through the different layers of a PCB, engineers came up with vias. The holes for component leads and contact points are drilled into the board using “via drilling”. This type of drilling can be traditionally done using a drilling machine or more modernly with a laser.
What is Via Drilling and Why is it Important?
Prior to automated computer software, the board was made using point-to-point wiring and a drill press, which was not only tedious to design and wire but led to a lot of short circuits and wire junction failures. With the advent of automated laser drilling machines, the thousands of holes that are in each board, are drilled at a rapid rate without the need for point-to-point wiring. These thousands of holes, if plated, are called vias.
Vias are really a fancy name for copper plated holes spanning through the different layers of a given board or panel, they are the entrance locations to the subway stations of you will. Having those multilayer boards has enabled electronic design to minimize the size of boards immensely without compromising on the complexity.
A via PCB board has a large number of connections, traces, and “tight” designs. This is what allows for smaller PCB boards to exist while still maintaining the complicated designs needed for functional purposes.
Vias can go through all layers of a certain board or they can be between certain layers only and not through the entire stack up (blind Vias). Since the signals move horizontally through the copper traces and vertically throughout the different layers through vias then you can think of vias as the Mario Bros tunnel entrances, they take signals places!
LPKF lasers are able to drill in the following materials.
- Substrate or FR4: This is the base material of the board, often being fiberglass. This is how the board stays rigid yet flexible. Printed circuit boards can have different thickness levels, but generally will be about 1.6mm. If you have a cheap PCB board on your hands, it will smell when you try to solder to it and it will not be flexible at all.
- Copper: The next layer is a thin copper foil which is laminated to the board using heat and an adhesive. PCBs can have anywhere from one to sixteen layers of copper and the copper thickness may vary.
- Solder mask: This is the layer that you see typically as green. It is placed over the top of the copper layer as a way to insulate the copper traces. This prevents accidental contact with other metals or conductive bits. This ensures that the right places are soldered properly. Typically, you will see green or red solder masks.
- Silkscreen: This is the white layer that you see on top of the solder mask. This is what allows your board to have symbols like letters and numbers. This is added in as a way to better understand the different areas of the board.
How do they get drilled?
Initially, those holes were drilled through boards by mechanical drill machines of course, but soon enough, technological demand rendered that technology nearly obsolete. Mechanical drills were slow, had low aspect ratio hole sizes, they left too much debris, and inferior edge quality. That’s when laser drilling became the way to go.
There are three ways that a board can be drilled through:
1. A through hole drilling machine will create through-holes that will connect all of the alternating layers of the board. This means that both the top and bottom layers, as well as the middle layers, will be completely drilled through.
2. The internal layers found in a multi-layer printed circuit board are connected by buried vias, or drilled holes that only connect the inner layers, never the exterior surfaces.
3. A blind via drilling machine will connect the top and bottom layers of the board to the internal layers but will not penetrate through the entire board.
The neat thing about printed circuit boards is that you will see a combination of both through-hole drilling and buried hole drilling. The reason that you will see both types of holes drilled is for the fact that PCBs are stacked, so the layers need to be drilled through to be properly connected via the circuitry.
The challenge with via drilling is that the laser must drill through the first layer without damaging the layer underneath. This is why automatic computer-aided drilling is such a popular option for PCB design.
With laser drilling, you can drill vias as small as 40 microns in diameter. You never have to worry about drill bit wear or break off, the process is clean and free of debris, the via edges are consistently sharp which allowed for ideal copper plating and, most importantly, the sheer speed of laser drilling is much faster than mechanical drills.
With new boards averaging between 5k and 50k vias and drill locations, it will be very inefficient to use conventional drills. After all, laser is a beam of light, and nothing beats the speed of light!
We meet this need by providing laser cut parts within .0005″ (12 micron) tolerances.
The motion system used on our UV laser systems is second to none in the industry, remaining stable year after year to ensure that the last batch is just as accurate as the first.
What are the Advantages of Via Drilling?
Although laser via drilling has a lower drill speed when compared to traditional mechanical drilling options, it has several advantages in that it can drill holes in circuitry that has a dense design and it allows a printed circuit board to be stacked in multiple layers reducing the need for one large single layer.
Other than this, the laser used on the blind via drilling machine or the through hole drilling machine can be controlled in a precise manner so that the internal copper layers are not touched. Finally, when a laser is used via drilling, the positional accuracy of the laser and thus the holes are significantly better than other forms of traditional mechanical drilling.
For those who are interested in via drilling lasers, the UV Laser can drill through two hundred drill holes per second, whereas the UV Laser can do eighty drill holes per second. Typically companies will use the UV Laser combination as it has high flexibility when it comes to opening up the Cu surface of the board while maintaining a high drilling speed.
How can we help you?
Our customers not only save on product costs but also receive lower emissions tests, improved fuel efficiency and noise reductions. Laser cutting Kapton and other typical flex materials on UV lasers yields a virtually carbon free cut and burr-free edges that will ensure your contacts are clear and plating will take.
UV lasers operate at a very high power density, allowing us to vaporize the material in micron increments with a beautifully collimated beam of less than 20 micron diameter.
A-laser runs three shifts to make sure we stay ahead of capacity and are able to be responsive to the most demanding turn-around times. Our ability to support our entire laser cutting service customer base is a direct result of the team’s commitment to excellence in all aspects of the work from data prep to quality control.
If you have a project that requires drilling of many micro holes or vias through multiple layer stack-ups then you need to consider laser drilling. With our new LPKF Microline 5280 laser system, we can give you the best quality drills with phenomenal lead times!