there’s a component so useful it’s in
every single piece of electronics
it’s so ingenious it’s been almost
unchanged since world war
ii it’s so important that every
electrical engineer learns to design
them
you won’t find this component anywhere
on a board because
it is the board i’m zach friedman
welcome to voidstar lab and today we’re
asking a big question
about something that everyone takes for
granted why are circuits on boards
anyways
every modern electronic device whether
it’s nuclear powered space probe from
1977
or a self-balancing rideable beer cooler
from 2020
has at least one printed circuit board
at the center it’s the most ubiquitous
electronic component of all
it’s the technology that literally holds
the world of electronics together
the printed circuit board you might have
noticed that electronic components have
become
a little more advanced over the last
century this is a capacitor from the
1940s
it’s made of foil and paper soaked in
electrolytes
this is the modern version it’s made of
metallized film and a gel electrolyte
electrolytes they’re what electrons
crave this is intel’s
cutting edge 1971 processor that
features a whopping 2250 transistors
here’s the 2020 model with about three
and a half billion transistors
this is a printed circuit board from the
1950s it’s made of copper on fiberglass
this is a 2020 circuit board made of
fiberglass
and copper once upon a time there were
no boards at all
manufacturers glued or screwed
components directly to the device’s
chassis
and then soldered the wires to each
other point-to-point soldering made
early appliances possible but it was
crude
that web of twisted leads was not a good
use of space it took a lot of manual
labor to assemble it made complex
circuits diabolically snarly
and it gave fork wielding toddlers a
buffet of options to zap themselves into
the shadow realm
as time passed devices grew more
complicated and wire wrapping was
invented to cram more parts
into the same amount of space
technicians stuck the components through
a perforated wiring board literally just
a board with holes
and they used power drill to wrap little
wires around each of the leads
they routed the wire where it had to go
wrap the other end and bam
connection made it looks nice and tight
on top
but on the bottom
this brings us to world war ii america
had to shove a ton of electronics into a
bomb
this big wire wrapping and
point-to-point soldering were not only
too bulky they were far too
labor-intensive for wartime production
instead the army screen printed metallic
paint onto a pair of ceramic discs
and soldered parts in between them this
didn’t just speed up production this new
so-called printed wiring board was more
compact
more durable it was easier to repair and
it was harder to short
and these are all features that you want
in a warhead by 1943 in the thick of
world war
ii the u.s of a had covered the country
in an entire industry of board
fabricators just to make more of these
fuses
anyways a couple years passed america
stuck 32 electronic detonators in a
different kind of bomb
and we ended world war ii as the war
machine unwound the birthplace of the
stuffed crust pizza found itself dotted
with a network of large-scale circuit
board manufacturers who had just lost
their biggest client
soon cheap printed circuit boards were
making their way into industrial and
then consumer products and a lot of
former professional wire rappers were
were checking the help wanted ads pcbs
really electrified the electronics
industry
before you needed an entire factory full
of artisan wire wrappers and
professional solderers just to
manufacture a piece of electronics but
now
all you needed was a stack of boards and
a river of solder
companies could suddenly produce a wider
variety of products pack them with even
more components and sell them at even
more affordable prices
parts manufacturing absolutely exploded
to keep up with this demand which
enabled
even more consumer products and that in
turn begat even more demand
and even cheaper parts the next thing
you know you’re watching youtube in the
bathroom and you forgot to wipe
since 1943 electronics production has
become way cheaper
safer easier and sexier but at the end
of the day circuit boards are basically
the same today as they were back then
they might be more angular and more
green but a printed circuit board is
still
a thin stiff board with copper printing
for your circuits
let’s snoop around these are the traces
which carry electric current just like
flat wires
this is a via a little tube shaped wire
that connects a trace on top of the
board with a trace on the bottom
this is a through-hole pad and this is a
surface mount pad
components get soldered onto these pads
to connect them to the circuit
but the board also physically carries
the components too
soldering a component onto the board
makes a mechanical connection
as well as an electrical one the board
itself is made of an
insulating high dielectric material that
means it doesn’t conduct current
or allow high voltage arcs to punch
holes through it the first commercial
circuit boards were made of cardboard
hardened with phenolic resin
it turns out that running electricity
over paper soaked in tree sap
is actually a really bad idea nowadays
we usually use
fiberglass because it’s tougher and it’s
heat resistant
in fact the most common material
is called fr4 that’s flame type 4 which
actually extinguishes itself if it
catches fire
fun fact nearly every modern circuit
board actually fluoresces green under a
black light
the manufacturer mixes a
glow-in-the-dark dye into the fiberglass
so that assembly robots called pick and
place machines
can easily see the board pick and place
machines are really cool
and they’re going to get their own video
and if you want to see that video
call to action subscribe and hit
notifications
the board begins life as a sheet of
copper clad that’s a
stiff backside with copper foil glued to
it that covers the entire board edge to
edge
the pcb fabricator aka the fab house
draws the circuit onto the board using a
chemical proof paint called resist
then the board is dunked into etching
which dissolves the exposed copper
only areas covered by resist stay on the
board a technician washes the board off
drills holes for the components and bam
printed circuit board
back in the day an engineer would
literally paint the traces by hand with
a brush
onto the screen used for printing this
is why old school circuit boards have
those whimsical curvy traces and those
teardrop shaped pads because those
organic shapes are easier to paint
artwork for modern boards with all the
angles is generated by an eda program
that’s electrical design assistance
instead of by a steady handed engineer a
photolithographic printer applies to
resist
and a computer controlled cnc mill not a
grizzled chain smoking machinist
drills holes in mills slots but what’s
really neat
is that even though the manufacturing
has become a lot fancier modern pcbs
are still like old school pcbs they’re
still thin
stiff cards they got copper printed on
them they got holes drilled in them and
we stick stuff to the copper
since world war ii we have made some
improvements the most important is
solder mask which is this enamel like
paint
protects copper traces from corrosion
and prevents stray solder from shorting
circuits
that was a tongue twister most circuit
boards are green because they have green
solder mask it’s
it’s just it’s just green paint is that
a letdown
on top of the solder mask there’s
markings part numbers etc
called an overlay it’s screen printed on
to make life easier for jabronis like us
to hack stuff one set of wires is nice
but what if we need even more wires
let’s double the fun by putting another
set of traces mask and overlay
on the bottom side too now we got
ourselves a dual layer board
need even more wires just laminate a
bunch of extra thin boards together into
a scooby-doo sandwich
and you got yourself a multi-layer board
[Music]
most modern devices actually still use
double layer boards because they’re
cheap
but some pcbs like the ones in computer
motherboards can have more than 20
layers
so now we need to connect these layers
of traces together
solder a wire from the top to the bottom
nah drill a hole and electroplate it
yeah the same way that steel rusts
exposed copper will corrode in air we
might as well gold plate the entire
board while we’re at it
i love gold finally those big
through-hole components with those wires
that have to be jammed through
holes yeah they got to go we replaced
them with teeny tiny surface mount
components that use conductive pads on
the ends
this is called surface mount technology
because they’re soldered directly to the
surface of the board as if the solder
were glue
they don’t have wires that punch through
the board and get soldered on the other
side
manufacturers continue to make ships
smaller even as they cram in more and
more features
some parts now have so many signals and
need so many wires
they can’t physically fit the pins so
we’ve changed the connecting pins from
metal tabs around the edge of the chip
into a grid of metal balls on the bottom
of the chip these ball grid
area parts can expose hundreds of
electrical signals and only a few square
millimeters
so modern boards need ultra thin traces
that run in three dimensions
just to spread those signals out far
enough to wire up the part
but what about those fancy flexible
circuit boards the kids keep talking
about will we ever be able to roll up
our ipads and smash a mosquito with
flexible circuit boards are actually
really common nowadays the only
difference between a flex board and a
rigid board is that the flex board
replaces that fiberglass with layers of
a thin heatproof
rugged plastic called capton flex pcbs
are way thinner than fiberglass and you
can integrate cables
into the board itself flex pcbs are
great for bending around obstacles and
for tucking electronics into nooks and
crannies
what they’re not very good at is flexing
the first problem is that the board can
bend
but the components can’t the second
problem is that flexible pcbs take
damage every time they wiggle eventually
the layers of plastic and metal will
delaminate and the board will peel apart
the thicker the board is the more it
strains when it flexes
so we can’t pile up multi-layer flex
boards the same way we can stack up
rigid boards
modern devices combine a stiff main
board that has the most intricate
circuitry
with flex pcb cables and modules
wherever the engineer can tuck them
flex pcbs are really designed to flex
just a single time
and that’s when the device is assembled
but can’t we just go back to sticking
components right to each other
or even integrate every single component
into one giant mega chip
that way we could trim off most of the
board and make the device that much
smaller
well not really the ability to put off
the shelf parts on custom boards
even though it makes the part a bit
bulkier it’s actually a good thing
modern devices have a lot of parts you
got processors
memory modems transceivers sensors
secret government espionage chips
security chips to protect you from
secret government espionage chips and
blinky
blinky lights getting all those
manufacturers to combine all their parts
together
would be an absolute nightmare and even
if you managed to pull it off you’d
never be able to make any design changes
because everything’s fused together into
one chip
integration is risky the more stuff you
cram into a single package the higher
the odds that a single defect breaks the
entire thing
stuff breaks if everything is in one
place the device is impossible to repair
this is still a big deal like some
hardware is always dead on arrival and
it’s cheaper to
repair it than to replace it
manufacturers have also stopped making
super low-end devices because
they can refurbish last year’s model and
sell it at a discount
if everything was integrated into a
single part that wouldn’t be possible
on top of that integrating everything
makes you your suppliers [ __ ] because
all it takes is a single supplier to
threaten to revoke their license and
your entire product
is trashed some components need to
maintain social distance from other
components
antennae for instance pick up
interference unless they’ve got
breathing room
and a high voltage board like this power
supply arcs will
jump between traces and blow up unless
they’re a certain distance apart
some parts also need special packaging
this is a pressure sensor that needs a
little breathing hole to allow the air
to flow in
this is a pulse oximeter that’s in a
special glass capsule so that it can see
the skin clearly
there’s just no getting around it you
need a bunch of parts to make
electronics
the best way to put a bunch of parts
together is on a board and the best way
to make a board is to print it
no matter how many parts are in your
design no matter how exotic they are and
which suppliers are involved
pretty much anyone can put anything into
any project as long as they can mount it
on a pcb
any parts can be combined in any
configuration and you’ll always know
you’ll have this thin
sturdy board keeping everything together
with convenient mounting holes
integration is kind of happening in a
way but instead of putting every
component into one chip
manufacturers are integrating many
components into one module
for instance the camera module
compresses images the fingerprint reader
handles your security
the display has the drivers embedded
right into the glass
the wireless modem processor ram
graphics chips are all
integrated into a single part this is
really the best of both worlds because
the manufacturer has already done a
bunch of your engineering and if
something breaks
you just replace the module this is
great for the user because like
anybody with a screwdriver can replace a
broken camera if the new one just pops
into place
so what’s the future of the pcb are we
still going to be using copper and
fiberglass when brooklyn is under eight
feet of water
yeah i think we i think we probably will
the the pcb production process is just
so well established and so
cheap that like boards are already as
accessible as they ever need to be
there have been some nitty-gritty
technical advancements like you can have
a sheet of aluminum laminated onto your
board to help spread heat
you can add plugged vias which are sort
of vertical wires
to route super duper dense components oh
and now you can get full
color silk screen electronics are
becoming cheap enough that we can
actually embed them straight into some
devices
this is a bunch of rfid tags which are
a tiny foil antenna and a teeny weeny
microcontroller built directly into a
sticker
these things don’t need a circuit board
because the sticker holds the thing
together
your [ __ ] might have also given you a
special bank card that displays a
security code and that is also an
electronic device with no circuit board
the
electronics are embedded directly into
the plastic of the car
there are some interesting rumblings in
the hackersphere toxic chemicals and
electroplating tubs are kind of
impractical
3d printed circuits are this idea that
just won’t die
the idea is you print the circuit board
out of regular plastic
and then you print the traces on top of
it using a special conductive
material there’s also the inkjet circuit
maker which
uses a basically modified inkjet printer
to draw the circuits on a sheet of paper
using conductive ink made of silver
finally you have the desktop board mill
which is like a tiny cute little cnc
machine that you put on your desk
and Shenzhen Eastwin it mills you circuit boards out of
copper clad cnc board mills have
recently become affordable and practical
and if you’re okay with the lack of
solder mask you can make simple boards
right there on your workbench give me
2500
and i’ll do it on video but what about
the super sci-fi
future well there’s vitrionics or
embedding electronic components into
panes of glass
this is already used to make capacitive
touchscreens for cell phones and those
super thin oled
televisions if you want to make
transparent electronics this is how
you’ll do it
after you invent a transparent battery
of course there’s also optronics which
replaces traces carrying electricity
with fiber optics carrying light
these could run way faster and way
cooler
temperature and awesomeness but there
are severe practical problems that have
to be overcome
the main one is that even though you can
easily send data through a fiber optic
line
you can’t send much power so ironically
you’ll have to run wires in addition to
your fiber optic traces to feed power to
the chips
[Music]
data yes what happened
any answer would be mere speculation
decades of experience have proven that
the best shape for a circuit is a board
and the best kind of board is a printed
circuit board printed circuit boards are
still the most common electrical
component even
though they’re basically unchanged since
we use them to blow up the wormoc
i think they’ll maintain their position
as the literal foundation of electronics
deep into the future hopefully you’ve
learned something about how they work
and why we use them thanks so much for
watching and i hope i’ve inspired you to
bust open your electronics
dig into the pcbs around you are you
interested in exactly how
engineers design these things maybe
you’re really interested in those
part-placing pick and place machines we
talked about earlier well i make videos
about all of those if you like the sound
of them
apples why don’t you uh why don’t you
give me a little subscription thank you
so much for watching voidstar lab is
still a new channel and every single
view and comment gives me the warm and
fuzzies
may your boards not catch fire unless
you want them to
i’m zach friedman this is void star lab
and i’ll see
you in the future
you