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Understanding Through Hole Land Patterns

August 17, 2020Viktorrine Ira

What is a punched hole? Should I use the drilled hole diameter or the finished hole diameter? I bet you’re thinking of those questions when trying to create your PCB land pattern for a through-hole component. 

At SnapEDA, our engineers analyzed different through-hole land patterns to produce the best libraries you can use for your design. Here’s a guide to help you select a through-hole pattern that best fits your PCB design. 

Drilled Hole vs. Punched Hole

Some land patterns suggest 2 hole diameters, punched hole diameter and drilled hole diameter. These diameters are the recommended sizes you have to follow based on the the kind of hole-formation method used during manufacturing. Their names itself basically explains the method. Drilled holes are formed by loading a drill bit to a cutting/drilling machine or a mini hand drill. Punched holes are formed by using a die set and putting pressure to the board using a punching machine. Although it is easier to produce holes in different shapes using the punching method, the commonly used method is the drilling method. The drilling method has a faster processing time and it is more applicable and flexible to use for different kinds of boards.

Finished Hole vs. Drilled Hole

Most land patterns only state the recommended drilled hole diameter but there are instances when the datasheet states a finished hole diameter as well. If the finished hole diameter is given, we recommend selecting this hole size instead of the drilled hole diameter. When given these 2 options in the land pattern, the drilled hole size refers to the drill bit size recommended for manufacturing. The finished hole diameter is the recommended hole size for your PCB land pattern, it’s the reduced size when the through-hole is plated. Board manufacturing industries also prefer to get the finished hole diameter and they’ll be able to determine which drill bit to use.

Through Hole Wave vs. Through Hole Reflow

There are datasheets that offer 2 recommended PCB hole patterns based on the mounting methods, one for Through Hole Wave soldering and another for Through Hole Reflow or Pin-In-Paste method. To select your hole pattern, you should first understand the mounting method you’ll be using. Through hole reflow uses a pin-paste or paste-in-hole technology wherein a solder paste layer and stencil is added to your through-hole design. The board with the solder paste is then being heated and the solder reflows to the terminal. After the heating process and once it cools down, your component is now mounted to the board. Through hole wave soldering is a more common mounting method for through hole components. The components are glued to the board, solder flux is sprayed to it and it passes through a heating machine where the solder melts and forms a wave which bonds the components to the board.

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