![]() ![]() The barrels of the vias will still be plated with copper the same as any other via on the board, the only difference is the empty air in barrel is replaced with the fill material. Because of this, conductive filled vias are not recommended for Via In Pad processing where the purpose of the fill is the reinforce the stability of the copper pad that is plated over the hole.Ī common misconception is that a non-conductive fill will either not pass any or only a very weak electrical signal through the via. Metal will heat and expand much more rapidly than the surrounding laminate and this may cause fractures between the pads and hole wall. The main drawback to conductive filled vias is the difference in CTE (Coefficient of Thermal Expansion) between the metallic fill and surrounding laminate. The metallic nature of the fill will naturally wick heat away from the chip to the other side of the board in many ways like a radiator. These can be found under chips that will be giving off a lot of heat where overheating is a concern. Generally, a conductive filled via will be used when heat or a large amount of current needs to be carried from one side of the board to another. You now have a solderable surface mount pad that also passes signal to inner layers eliminating the need to rout the signal to a via on the surface layer.The newly plated copper surface is flattened and smoothed (planarized) to be even with the surrounding copper features.The surface of the plugged via is then plated over with copper.Conductive material can be used but it’s not recommended since conductive material expands much more quickly than the surrounding laminate when heated which can cause cracks and pad failures during the assembly process. Fill the via with non-conductive material. ![]() The following steps are taken in this process. TIP: We need to know the location, qty and size of the holes that need to be Via In Pad. Make sure this process is called out in your fab notes. This allows much simpler routing by soldering directly over the via. Rather than using the standard “dog bone” land pattern to transfer signal from the BGA footprint to a via that passes signal to other layers, vias can be drilled directly into the BGA footprint pads. This process is becoming more and more common as BGA packages are becoming tighter. ![]() Otherwise we may put the order on an engineering hold to verify your intention. TIP: If you are tenting some of the vias in your design, always make a fabrication note either in a readme.txt file or Gerber fab drawing so we know you have intentionally removed the mask clearances from some of your vias. ![]() 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. Smaller diameter vias (12mil diameter or less) have the best chance of remaining closed. Tenting a via will sometimes result in the hole remaining covered but it isn't guaranteed. No special steps are taken to ensure the hole opening remains closed. Tenting a via simply means to cover the annular ring and via hole with solder mask. Simply remove the mask clearances from the vias you wish to have tented. This is the easiest and least costly process-actually there is no added cost for this process. First, let's start with defining these terms since they can be frequently misused and misunderstood. There are many reasons a printed circuit board designer might want to have a via tented, plugged or filled. ![]()
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