Circuit boards have all these tiny components on them, but how do they actually get there?
Today, we're gonna see how circuit boards are assembled by the professionals.
[Music]
Thanks to PCBWay for sponsoring this video, and giving us access to explore the factory.
Now I'm no stranger to soldering small components, but I'm mostly self-taught and honestly making it up as I go along.
I want to see how the pros do it, and not just for one board, but for thousands.
And how do they make sure that each and every board works just like it should?
It turns out they use robots and unicorns and rainbows...
Okay, one of those is a lie, but the other are totally real. And they're amazing, so stick around.
This is the basic problem we're trying to solve: We're trying to get all these little tiny components...
This is one of them here on the tip of the tweezers. Here It is next to a grain of rice.
Trying to solder those onto all the little copper pads on this board, and we've got to get them all in the right place,
all aligned just properly, with the right amount of solder paste, and we have to do it correctly every single time.
This is a surface mount assembly line.
Surface mount components are the little ones like this that sit on top of the board. Just like that.
And through-hole components are the ones that go through holes in the board, with wire legs like this.
Surface mount components are used whenever possible these days for commercial products, because they're
way easier for robots to handle and deal with, but we still need through-hole components sometimes,
and they're a real pain in the neck for the factories to deal with. We'll talk more about that in a minute.
The first step in the surface mount soldering process is applying the solder paste.
This is a solder paste stencil machine.
It applies solder paste, which are these microscopic balls of solder, suspended in a flux paste.
When we heat the solder paste up in an oven, it flows into liquid solder, and then hardens as metal,
and makes a good electrical joint.
We only want the solder paste to go on these pads, where the components are going to be soldered down.
So we use a solder paste stencil, which is a thin piece of stainless steel with laser-cut holes,
where the solder paste is gonna go.
And then, the machine pretty much just squeegees on the solder paste, very similar to how you would for silk-screening.
There's a fair bit of art to this. Sometimes you have to adjust the holes in the solder paste stencil,
to get the right amount of solder paste in all the right places.
This over here is a solder paste inspection machine.
They're super high-tech.
This is the first one I've ever seen, so I wanted to invite Mr. Chen, the manager of the factory to explain...
maybe you can explain a little bit about how this works, and why do you guys use one?
-Thank you very much. Mr. Chen -You're welcome
So this machine, this is my favorite machine for all of surface mount, for this whole factory.
This is a pick-and-place machine.
It's a robot that takes all of the little parts out of reels here, and
puts them on the board, in the solder paste that has already been applied, and it does it really quickly.
The components come to the factory on reels like this.
They're in this plastic tape that has these little wells.
One well per component, and then it has sprockets all along here, for where it goes into the feeder in the
pick-and-place machine, and it has a sprocket that advances it with the sprocket holes,
so it feeds one component at a time to the pick-and-place head.
Mr. Chen and the technician are gonna show me how to load it here.
Put it in here... that's gotta go up through here, okay...
and then this under here? -Under here.
Oh, under there.
I'm not very good at this yet.
And so then this just pulls here, and this feeds.
Okay. So there we go.
Now we've got--so we basically loaded the end of the tape,
which didn't have any components in it, it was empty.
And now we're right up to where there are components, right?
So this, would then get pulled out of here, and put in here?
Yeah, finished.
That's pretty cool.
Now it's time to actually place the components,
and we come over to a different machine that has a few extra features.
Accuracy here, is key.
And there's a couple different things that help with that.
Specifically cameras and then fiducial marks, which are registration marks on the circuit boards.
So, fiducials are these little marks that the designer puts on the board,
they're usually round circles with a dot in the middle,
and there's a camera on this head, and when the board first comes in, the camera looks for that mark,
and it looks for a couple of them, and once it knows where a couple of those marks are exactly,
it knows how is the board positioned both, you know, forward, back, side to side as well as rotation.
And that's key, because we want to know within that board
Then we can calculate where all of the positions of the components should be.
The second thing, is... so this head has a vacuum tip on the end of it.
And that vacuum tip comes out and it picks up a component, right? Just using suction.
We need to know exactly where that component is.
For small components, we can just kind of guess it's on the end of the tip.
But for big components, they may shift slightly.
So there is a bottom camera on this machine that wasn't on the other machine.
That bottom camera takes a picture, so it moves the component over, and then it takes a picture
upward of the bottom of the component and they could see exactly how it's rotated or shifted, relative to the head.
Once we know the board position and the component position, then we can precisely align them
before it drops the component onto the board, into the solder paste that's already been applied.
And it can do this really, really quickly.
Some of these machines in this room can place over 40,000 components an hour.
And hopefully, it gets it precisely right, every single time.
They've actually got three separate machines here back-to-back.
Once a board is done with all three, it should have all its components placed on,
at least all its surface mount components, and it comes out here for visual inspection, and any hand rework.
So, occasionally a component will be just slightly misaligned, or it needs to be nudged over.
So she's checking each component on the board,
just visually inspecting to see if anything looks wrong,
and then somewhere she's got a pair of tweezers and she's been occasionally nudging something around
just to fix it a little bit.
Finally, it's time to actually melt the solder!
So this is the reflow oven.
You can think of it like one of those conveyor belt toaster ovens
You see in like hotel buffet lines,
but it's much bigger and it's a lot fancier.
So the idea here is that,
we want to raise the whole board, and the solder, and the components all up
gradually on a temperature curve to a maximum temperature where that solder melts,
and then gradually cool them off on a specific curve.
So the boards come through on the conveyor belt all the way through the reflow oven very slowly
It's bringing them up to temperature, down... Once it comes out this end, It's completely soldered. It's then inspected.
So, do a quick visual inspection and then it goes into...
One of the cooler machines in here. This is an AOI machine, which stands for Automatic Optical Inspection.
So it uses all different colors of rainbow light to automatically inspect all of the different solder joints.
What we want to do is we want to look at every single solder joint that came out of the reflow oven,
and see if it looks correct.
So, what they do is they- they first take a board that they have tested and visually inspected that they know is like
a Golden Master, it's perfect. And they go through and they take a whole bunch of pictures of
every single solder joint, using all of the rainbow light inside the machine, that's shining at different angles.
So they've got different colored lights, at- shining at different angles,
so that it causes the shiny solder, which reflects the light, to light up in all different colors, depending on the angle of the solder.
So it allows them to visually, from one angle, using a two-dimensional camera, to see in three dimensions this shiny surface,
based on what color is reflecting off of it.
The machine then knows what are the colors for all the different solder joints for that golden master? What do they look like when they're correct?
And then, it takes a picture of the board that's currently being inspected, that he's looking at right now,
and you can see there was just a bit... you can see right here. He just found a defect, right?
So this component is shifted, and it does not look like this. You can see the machine caught that and said, "There's a problem here, go look."
And so, he's manually looking through all of the components to see which ones look wrong to him that the machine said,
"Maybe these are not quite right," and then he's putting these little inspection arrows to say,
"Hey, this needs to be fixed," and someone will come by and fix that with a soldering iron in the rework room.
And then, he's putting an X on that board to say, "Hey, here's a problem."
This allows them to really make sure that all of the solder joints are correct, and it's way faster and more efficient than
doing it all by hand, by just staring at the board looking at every single one, by hand.
But my favorite kind of defect that they find is called tombstoning.
It's where a small surface mount component is flipped up on one end and it looks like a tombstone in a graveyard.
And actually... they don't generally have that problem here at this factory,
we had to get them to rework one of their boards and flip one up manually, so that we could show what it looked like.
This is a X-ray Machine, and they use this when they're doing BGA soldering,
where all of the the pins for the chip are underneath the chip.
This is an X-ray of the top of the chip, and these are all the little balls.
This is the sign of a really high quality PCBA Factory, that they can do BGA like this, and inspect every single one,
to make sure the solder is correct, and that it's not, you know, connected together, or smeared,
or they've got not enough solder, or they're missing a solder ball, or they got an air bubble, or something like that.
It's super cool. I've not seen one of these before. This is the first factory that I've been to that's had one.
One of the really important things is to make sure that they're putting the right components in the right place on the board,
and with all the reels and feeders and pick-and-place machines, it is possible to get that a little screwed up.
A lot of the components look exactly the same.
So what they're doing in here is they're testing the value of every single component on a board
that's had all the components placed by the pick-and-place machines,
but before it's been run into the reflow oven, so they're not soldered down,
and so she's going through and with these tweezers, picking up every single one of these components,
specifically the resistors and capacitors, which all look the same, and making sure that they're the right values.
And my understanding is this is a pretty unique machine.
So Mr. Chen, this is not a machine that every factory has, right? This is something special.
That's awesome. Super cool piece of machinery. I've certainly never seen one of these at a factory before.
As you can see, there's quite a bit of setup and tweaking involved in running all these pick-and-place machines,
and inspection, and solder paste stencils and I would have thought, before I came out to the factory
that PCBWay would only be willing to do this if you ordered like a hundred boards, and otherwise
they would require you to do it by hand assembly.
But it turns out they're willing to do pick-and-place for even one board, provided you're willing to pay a setup
fee for them to program all the machines, and you have to buy a few extra components, because they waste
some components as they're loading the feeder, as they're peeling back that tape, a bunch of components come out, and so you've got to provide some extras.
But, provided you're willing to do that. they'll run their pick-and-place machines for just one.
Otherwise, they've got a service to do hand assembly of circuit boards, and so let's go across town to their other factory to see how they do that.
[Music]
This is where they solder prototypes by hand.
It's usually because they're only making a couple boards of this particular design, and it just doesn't make sense
to set up all of the machines and tweak everything.
This is pretty much like what you would expect.
If you've ever soldered a board at home this pretty much works the same way, he's got a BOM, or Bill of Materials here,
that's just a spreadsheet that has all of the part numbers, and then all of the numbers on the board
So it'll be like, you know R21 for the 21st resistor. The designer will put that on the board,
it goes onto the silkscreen, which is the white lettering on a board.
He's basically just taking all the parts out of bags, putting them in the right hole, making sure they're turned
the right way around, and soldering them just like you would at home.
But what happens when we have a ton of boards?
Let's say we're making 100 boards, or 1000 boards, or 10,000 boards, and we have a ton of through-hole components
What do we do then?
It turns out there's a really cool answer, but we gotta go back to the other factory to see it.
These workers are all stuffing different through-hole components into the board. Each one's doing a different component, or two components sometimes.
This is the cool part though. This is the wave soldering machine. This is a giant pool of liquid solder.
And so the idea is that the boards come along over the top of the liquid solder, and the liquid solder, in a wave,
splashes on the bottom of the board, and it sticks to anything that's metal. So that is the metal pads on the board,
but also the the metal legs of the components, and it creates these nice tent-like joints between the two.
Now, it doesn't stick to the green solder mask, which is exactly what the solder mask is there for.
It causes the the solder to run off, like water droplets running off of a piece of plastic, and thus
it only sticks to the areas we want it to stick to.
So I couldn't help but notice this really cool robot you guys have. What is this for?
Ahhh... okay, and you push this button?
[Excited laughter]
I love it! That is so cool. And you guys made you made this yourselves, right?
That's really cool.
What is this for?
Oh, it's not plugged in.
[Music]
Oh, it sings! Oh, this is what was singing earlier. I got it. I understand now, this is so cool.
It is so homemade, and so like perfect for it's task. I love it.
So far, we've seen a lot of workers visually inspecting boards, but that just tells us how the solder joints look,
and that's not really what we care about. What we care about the most is do they work electrically?
And so we need to do some electrical testing.
For one-off prototypes, that's really the responsibility of the engineer to test their own board.
They may have made some mistakes in their design.
But when we start making a bunch of boards, we need a repeatable way of making sure it actually works
the way we intend it, and that's where testing jigs come in.
This is a pogo pin testing jig that is custom designed for this board. It's also called a bed of nails jig.
These here are testing pins that are spring-loaded
So these are spring-loaded pins here that touch custom designed test points on the board
that the designer designed into the board, and then this thing is custom-designed to match those test points.
These kind of all look the same, but they've all got a different layout of pins and registration pins
and board outlines, so that it fits in.
This jig will power up the board, will test that it works properly, and will also do things like program in firmware
into the microprocessor, it'll assign serial numbers, things like that. It can also assist with more functional
testing. So this is some sort of IoT device, and they've got a base unit for it to talk to, and there's a whole
test script that's programmed into the computer, so that the technician can test it all at once to make sure that
every step of the product is working properly.
However, sometimes you can't get around old-fashioned button pushing. This product doesn't happen to have
a button in it, but often this testing process involves a technician just pushing a button, making sure
the buttons work like you expect.
PCBWay also offers a service I haven't seen at any other PCB Assembly factories before.
This is a conformal coating machine. Once the board is fully assembled and tested, they spray it with a
waterproof, dustproof clear coating.
So, the one thing we haven't talked about yet is how someone like you can order your own board.
PCBWay has a website where you could upload your board design, specify all the components and
part numbers that you want, they'll take care of making the PCB and ordering all the parts for you.
Once the parts come in, they come into the warehouse here, where they collect them all, once they got everything
for your order, it comes over here to the verification area. She's checking to make sure that all the part numbers
are correct, all the values are correct, and that they've got the right number of everything,
If you'd like to order your own board, whether it's bare or assembled, you can go to PCBWay.com,
there's a link down in the description.
So, thank you, Mr. Chen, for taking all the time to show me all the cool stuff you and your team have built.
I really appreciate it. Thank you.
If you enjoyed this factory tour, be sure to check out the other factory tours on my channel.
We've also got a bunch more cool ones coming up soon,
so be sure to hit that subscribe button, and that little bell icon next to it, down below.
I'm Scotty with Strange Parts, I'll see you next time.