If you are an intuitive and well-read PCB designer, over the past decade, you have likely been introduced to the topic of via filling by well-known industry leaders who have covered the process extensively. However, if you are like me, you have to stub your foot on the machinery, and trip over the operators who run it before a snappy concept like via fill can become a personal reality. (I try not to apologize for this as most everyone knows that many PCB designers are visual learners, taking in knowledge less by reading and more by sight and touch of the physical parts and processes. Advisory: Ouch! This method can hurt sometimes.)

Fortunately, I took a wonderful detour from my 30 year long career path as a designer that has led me to work at a place where learning prototype PCB manufacturing by way of the senses is easy. At Prototron Circuits I am steps away from the materials, processes, and people successfully fabricating quality PCB prototypes that incorporate via fill technology.

Over the past few weeks, without personal injury, I have been able to fill my senses with a clear understanding of via fill by following a PCB through our shops' various processes, and believe me, there are many! Now I understand what I’d missed skimming through so many of those white papers! After examining the silky-gold coplanar surface finish covering those filled vias, I have to ask myself -- why aren’t more designers ordering via fill on their designs? Are the white papers describing via fill not getting through to the design community?

The answer: well, unfortunately there aren't any comprehensive white papers on ordering via fill. Don't despair! You don’t have to stub your toe, or bonk your head to grasp the understanding of this subject. I've already done it for you and I'm going to share with you how you can incorporate via fill on your next design by following four simple steps from Prototron Circuits.

It's simple, just remember SAND: Select, Assign, Note & Drill

1. SELECT which vias in the design will benefit from being filled. Such vias may be: stitching vias - dispersed vias within the boundaries of a component pin’s land, utilized for thermal dissipation or to increase current carrying capacity to adjacent conductor layers. Or they might be single vias placed within each of the tiny lands of a small ball grid array pattern. The criteria used to determine if a via is a good candidate for via fill at Prototron is to observe if its drill size is within a range of .008 [.20mm] -- .020 [.51mm] and is located within a land in which solderability would benefit from coplanarity – a smooth, geometrically flat land surface.
2. ASSIGN a unique via size. This will allow our CAM department to quickly identify the hole to be filled. For instance, if a common open via size in the design is .010 [.25mm], changing the hole designation to .009 [.23mm] for holes to be filled would work very well to differentiate the hole to our CAM department (as long as no other .009 dia open holes exist, of course.)
3. NOTE on the fabrication drawing a via fill specification. This is a key step in getting the board quoted and processed properly. Minimally, the note should specify the unique via sizes to be filled and Prototron’s via fill material of choice -- Taiyo’s THP-100DX1. (Conductive via fill is available. Ask us!)
4. DRILL file output -- specific to the uniquely assigned vias -- can be included as a separate file. This helps our CAM department to expedite your order. Filling vias requires a separate drilling stage from other holes so it makes sense that the output for the filled vias is provided as a separate file. Our CAM department can easily accomplish this step for you as long as your vias to be filled are identified with unique sizing per step two.

That's it. Four simple steps!

On your next project, why not let Prototron show you how our via fill capability can increase your design’s manufacturability, solderability, thermal dissipation characteristics and overall quality!