(upbeat music)
- Hi and welcome to Getting Started with KiCad.
I'm Shawn Hymel and throughout this video series,
I'll be showing you how to create
this custom board from scratch.
If you're curious, we'll be making a badge
that pulses a couple of LEDs.
The white area around the LEDs
allows you to draw or write something fun using a Sharpie.
That way, you can customize and wear your badge
with pride at your next event.
Don't worry, you can erase the Sharpie
with a little bit of rubbing alcohol.
I worked with my friends at DigiKey to make these videos.
Whenever I'm creating a custom PCB,
I always check DigiKey first for components.
In fact, we'll be using their site later in this series
to order parts for the board.
But first, let's talk about why
you would even want to make a PCB in the first place.
In the 1960s, telephone crossbar switches
like the one shown here,
used a wiring technique that involved
wrapping small-gauge wire around posts.
If we zoom in, we can see the individual wire wraps
and notice that no solder was used
to make these connections.
As electronics became more popular in the 60s and 70s,
the wire wrapping technique was adapted
to connect components together.
Wire wrapping is an art unto itself,
often resulting in striking and beautiful patterns
on the back of boards.
Even though wire wrapping could be automated,
it was still relatively expensive and time consuming.
In the 1980s, surface mount technology
was gaining in popularity,
which ultimately resulted in electronics
that were faster and cheaper to produce.
Prior to surface mount, boards were made
with through-hole technology.
If conductive material is added
to the inside of a hole to allow for a better connection,
this is known as a plated-through hole, or PTH.
As you can see on this 1984 Sinclair QL computer,
the components were much larger
and had leads that poked through holes in the board.
You would generally need to solder the leads
to the board on the opposite side.
If you look closely at this raspberry pie,
you'll see that the electronic components
do not have leads that extend through the board.
Instead, the components are placed and soldered
on just one layer.
This is known as surface mount technology, or SMT.
Surface mount technology is great
when you're mass producing hundreds or thousands of boards,
but it can be a pain to solder by hand.
So, we're gonna stick to plated-through hole parts
for our board.
It just makes things a little easier.
Now that you know the history,
what is a PCB?
Well, it's an acronym that stands for printed circuit board.
It is a board or card that electrically connects
and mechanically supports electrical components.
These connections are made
with a series of conductive tracks or traces,
usually copper.
And this copper is laminated onto
or in between sheets of non-conductive material,
like fiberglass.
If you were to take a cross-section of a PCB
and examine it under a microscope,
you would see a number of layers.
The substrate is the rigid or semi-rigid material
that holds everything together.
Most PCBs you come across will use fiberglass
and cured epoxy resin.
The epoxy is normally flame-resistant
and likely meets the flame retardant grade four standard,
which is where FR4 comes from.
You'll often hear people refer to this material as just FR4.
A thin sheet of copper is pressed and heated
onto the substrate.
This would be a single layer board
which means that only one side of the board
has conductive material on it.
Another layer of copper can be added to the other side,
making it a two-layer board,
which is what we'll be using.
You can even add more layers of substrate and copper
to make multiple-layered boards,
but we won't need to worry about those for this project.
They usually cost more and are reserved
for more complex PCB layouts.
For our plated-through holes,
a drill bores out a chunk of copper and substrate.
A thin layer of copper is then added
to the inside of the hole
using a process called electroplating.
Note that this also deposits copper on all exposed surfaces,
so your main copper layer grows a tiny bit.
This small layer of conductive material
is how you can make electrical connections
between different layers of copper
and is known as a plated-through hole.
Copper is then etched or removed
from the top and bottom layers,
leaving only the traces and pads
that you specified in your design.
We could stop here and you would have
a perfectly usable two-layer PCB.
This board was made on a Bantam Tools PCB milling machine
where copper is milled or routed off the board.
I can easily solder components to this
and it would work well for a project or a prototype.
However, it can be nice to add a layer of protection
and help prevent short circuits
when you say, accidentally move a screwdriver
across the board.
So, a Solder Mask layer is often applied
on top of most of the board.
This normally consists of a lacquer-like polymer
and is only put on surfaces
where we don't want to solder components to.
It also helps prevent solder
from creeping down the traces or jumping between traces.
Traditionally, this is green, but ours will be purple
because that's just the way OSH Park rolls.
When designing our board,
we're usually worried about areas
where we don't want Solder Mask to be,
which we'll call Solder Mask Keepout.
These will usually be colored areas
on a layer around things like pins and pads,
places where we want exposed copper,
such as the top and bottom of our through hole shown here.
Copper can oxidize, which makes soldering to it difficult,
so most manufacturers will add a surface finish.
We'll have our board house use
an electroless nickel immersion gold,
or ENIG finish.
This gives any exposed traces or pads a gold color,
makes soldering easier and helps protect
the copper underneath.
Finally, many board manufacturers
will add a layer of ink in any pattern we want
to help us identify components,
name the board, or add silly artwork.
This is known as a silkscreen layer.
It's normally white, but sometimes a board house
will let us pick another color.
If we go back to our raspberry pie,
we can see the bare substrate,
which is brown or tan in color.
Some exposed copper,
which has been given a gold-colored finish,
green solder mask on most of the board,
and white silkscreen.
If you were to slice into the PCB
and look at a cross-section under a microscope,
you would find that the raspberry pie
has six layers of copper,
which is a lot more complicated
than the board we'll be making.
With a basic understanding of how PCBs are made,
let's talk about what it takes to design one.
These days, most PCBs are designed
in a computer-aided design software,
or CAD program for program.
While each PCB CAD program operates a little differently,
they all generally have a similar flow.
It's important to keep in mind
that KiCad is really a collection of programs
that work together to help you design a board.
The first step is to design your circuit
and this can be based on something you found online,
created in a simulator, or constructed on a bread board.
We won't cover circuit design in these videos,
as that's really outside the scope of building a PCB.
In fact, we already have the circuit designed.
It's just a 555 timer
that causes some LEDs to fade in and out.
Before we can create a schematic,
we may need to create custom schematic symbols
if we can't find some in the KiCad or DigiKey libraries.
We then draw our circuit
in the software schematic capture program,
which is known as eeschema in KiCad.
We can research the exact parts
we need on DigiKey's website.
From there, we can look at each part's data sheet
to determine what the footprint should be.
When I say footprint,
I'm referring to the configuration
of pads and holes on the PCB used to mechanically
and electrically attach components.
For example, these eight holes
make up the footprint for our 555 timer component.
If we can't find the footprints
for our parts in the libraries,
we'll need to create our own
using the KiCad footprint editor.
Then, we use cvpcb to associate schematic symbols
with footprints.
Still in eeschema, we generate a net list,
which is just a text document
that tells which pins are electrically connected
to other pins in the circuit.
We open up our board layout program, known as pcbnew
and set up our design rules
as specified by the PCB manufacturer,
which we can usually find on their website.
We then import our net list,
which places our parts in the program.
We move the parts around as we see fit
and draw copper connections, known as traces,
between the necessary pins.
After that, we generate a set of files,
known as gerbers, that represent
the various layers of the board we wish to make.
We can use the gerbview program in KiCad
to examine these files before we send them
to the manufacturer.
Finally, we create a Bill of Materials, or BOM
and order the electronic components from DigiKey.
Once all the parts arrive,
we can solder them to the board to build the badge.
There are a number of PCB layout programs out there,
but in this series, we'll be looking at KiCad.
KiCad is free and open-source,
which makes it great for learning
how to make your own PCBs.
But it's also powerful enough
to do more complicated work.
For example, the guts of this Olimex DIY laptop
were designed entirely in KiCad.
If you're following along with these videos
and you feel that you need some additional material
to help you along,
I highly recommend checking out
Chris Gammell's tutorials on KiCad,
which he titles Getting to Blinky 4.0.
Chris takes a slightly different spin
and shows a few different tools
which can be very useful when learning a new program.
Chris also helps run the KiCad forums,
which you can find at forum.kicad.info
Here, you can search for answers
and ask questions to the community if you get stuck.
All right, enough talking.
Let's go download KiCad so we can start making our board
on the next episode.
Head to kicad-pcb.org and click the big Download button.
Choose your operating system, which is Windows for me.
Follow any directions you might see here.
For example, I'll choose to download the 64 bit version,
as I'm running a 64 bit version of Windows 10.
Follow whatever instructions are necessary to install KiCad,
which could include running the Windows Executable,
installing the disc image on Mac OS,
calling APT-get in Debian,
or building it from source code if you're so inclined.
If presented with installation options,
keep everything the default.
Open KiCad and you'll be presented with the project manager.
We'll create our 555 timer badge project here
and begin designing our board.
But, that'll be on the next episode.
I hope this has given you some insights
into how and why PCBs are made.
Feel free to come back to this episode
if you feel that you need a refresher
on some of these terms.
See you next time.
(upbeat music)