Confused again ... pad size

OK … either I am way overthinking this or PCB’s are rocket science.

So … designing my first board (well at least in 20 years).

Think I have KiCad under control …

Needed a few custom components no in the library.

How do you go about figuring out the pad size?

These are all through hole parts.

The hole makes sense … did some reading … pin size plus .3 -.4 mm … easy

Now for the pad … and boy I got lost in reading here.

They start talking about manufacturing error … minimal annular ring before breakthrough …

I did see notes on things like do not exceed 3 mm or you need to think about changing the shape.

Formulas and manufacturing standards and …

This is a simple circuit … the fuses are only 300 mA so no high power stuff. 115 to 12 transformer …

So, for example … I need to use a special fuse holder (touch safe per the customer) … 1.2 pins or 1.5 hole.

Now, what size pad ?

The transformer and the input connector have had similar size pins (1.4 hole) and I went with a 3 mm pad … but this is more of a guess.

Now that the hole is getting a bit larger (1.5) I am wondering if 3 is too small ( and maybe it was for the other also)?

I am hand soldering this … don’t know if that makes a difference.

Just looking for some simple guidelines to follow.


Maybe this is helpful? How to calculate PTH hole and pad diameter sizes according to IPC-7251, IPC-2222 and IPC-2221 standards? - PCB 3D

I would generally follow the IPC recommendations for most cases (you may want to go larger than them if the component will be under mechanical stresses)

So basically for Level A (easiest for hand-soldering), it appears to be lead diameter + 0.95mm.

Sometimes the data sheet has advice on pad size.

Worth consideration:

Syntax (what things are called, from Parts, Symbols, Footprints, automobiles…) can mean different things to different Software.

Kicad Schematics use ‘Symbols’. The PCB’s use Footprints.

Symbols are simply a Graphic to represent something such as a DIP-socket. What it looks like only matters if you care that it matters.

Symbols can have a Link to a Footprint but, not necessary (it’s used only for the PCB).

Footprints can have a Link to a 3D-Model or WRL but, they are used for only the 3D-viewer - a pretty picture.

Pads can be of different shapes - there are several to choose from (if you double-click a Pad).

Size of the Pad depends on several things - Manufacturability, Current-load… Personal-Preference…

Stock-Pads on Parts are usually small but, can be re-sized/shaped.

Example: I CNC Mill my PCB and I like big Oval Pads. Holes size depends on the Part’s Pin’s/Contacts…

If making your own PCB, do what makes Common-Sense to you.

Make a Footprint with some example Pad/Hole sizes and that will trigger your thinking with better clarity toward the end-goal…

Way better example than I found … this one makes sense … Thanks!

This is what I am looking for … just a good “rule of thumb”. If is was a critical board it might be different but this a large board with few parts. Thanks!

Now milling is something I understand … I am a machinist by trade.

I think I am getting the hang of this.

I did find a symbol for a fuse but the for the pads, I needed a special fuse holder … so I started to draw one.

Got to sizing the pad and started way overthinking this.

“Common” sense is something I understand… just didn’t want to break rules that are in place for manufacturing.

Heck, wayyyyy back in the day (making PCB’s in my mom’s laundry tube) I would leave as much copper as possible as a heat sink and or ground plane.


PCB manufacturer’s have requirements commensurate with their manufacturing capability so, look at info on their site. If making your own PCB, consider that, whether you use:


there is always enough variability such that Bigger Pad’s are your friend…

How are you going to make this?

I am making a one off first for approval … they with some luck say 10.

Kind of a long story … I do a lot off odd jobs for this client … all industrial electric work (patch cords … push button stations … simple starter boxes).

They have a very simple air monitoring system (just a diff press switch … buzzer … relay … back up battery).

These boxes were designed 30 plus years ago … made by one guy (we worked at the same place for a while … both contractors).

He has long since retired … maybe even passed away … no one can get a hold of him.

The boxes are starting to fail … they wanted me to reverse engineer them and make a few.

Most of it is industrial electrical stuff but it has a PCB in it.

There are so few parts on the board … maybe 20 … that it is almost like making a kit when I was a kid.

They don’t want me to change the design.

Some of the parts are obsolete so I am just updating the ones I need to.

Anyway … I have made PCB’s but that was years ago. I downloaded KiCad … I knew I needed a Gerber file … just trying to figure out all the little details.