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Via Tenting, Plugging, and Filling

There are many reasons a printed circuit board designer might want to have a via tented, plugged or filled. First, let’s start with defining these terms since they can be frequently misused and misunderstood.To accurately drill your countersunk holes, we will need the following information.

Via Tenting

This is the easiest and least costly process—actually there is no added cost for this process. Simply remove the mask clearances from the vias you wish to have tented. Tenting a via simply means to cover the annular ring and via hole with solder mask. No special steps are taken to ensure the hole opening remains closed. Tenting a via will sometimes result in the hole remaining covered but it isn’t guaranteed. Smaller diameter vias (12mil diameter or less) have the best chance of remaining closed. The main purpose for tenting shouldn’t be to close the opening of a hole but rather, cover the annular ring to prevent exposure to the elements and reduce accidental shorting or contact with the circuit.



Copper Thickness FAQ

The most common unit of measure for the copper thickness on a printed circuit board is ounces (oz). But how thick is that? It’s the resulting thickness when 1 oz of copper is pressed flat and spread evenly over a one square foot area. This equals 1.37 mils (1.37 thousandths of an inch). Of course not everyone thinks in mils so please refer to the chart below to convert into your favorite unit of measure.

1 oz Copper Thickness Conversion *To determine the thickness of 4 oz, simply multiply 1 oz thickness x 4.  1.37 mil x 4 = 5.48 mils = 4 oz
1 oz
1.37 mils (thousandths of an inch)
0.00137 inch
0.0347 mm
34.79 µm  (micron/micro meter)


Most PCB’s are constructed with 1 oz copper thickness.  At PCB Universe, if we are not given specific specs, we will assume 1 oz when quoting and building your design.  If you have determined that your design requires more current than 1 oz can carry, you’ll need to consider increasing the copper weight or increasing the width of your traces.  Of course the thicker the copper the higher the cost, but there are certainly times where this is necessary.  The cost increase is not only due to the raw material costs but processing thicker copper weights takes more time and is a little trickier to do.  Keep the following chart in mind when designing your board.  The more space you can allow between copper features the better.  Etching the spaces (air gap) between traces is more difficult than etching a trace of the same width as your space.