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Electrical Component Cross Sections

Take a look at these fascinating and educational cross sections of an LED, resistor, diode, capacitor, and more. (The images in this Moment created by TubeTimeUS are licensed under CC BY-SA 4.0:

here's a cross section of an Ethernet transformer. inside a network adapter, there is one of these in between the Ethernet PHY chip and the cable, providing isolation and safety.

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here's the side view cross section of an Ethernet transformer.

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annotated version of the Ethernet transformer cross section.

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ok don't try this one at home: this is a cross section of an LR44 alkaline button cell! 🔋⚡️

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annotated cross section of the LR44 alkaline button cell.

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inspect this cross section of a BGA-packaged chip.

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annotated cross section of a BGA-packaged chip.

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detail showing the vias in the substrate

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ever wondered what's inside an optocoupler? wonder no more--look Kat this cross section!

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...and here's the annotations for the optocoupler cross section.

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diodes may look simple, but there's subtlety inside them. check out the cross section of this 1N914.

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here's the annotated cross section of the 1N914 diode. the two Dumet slugs are separate pieces of metal from the leads, and are brazed together during manufacture.

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look at the slug on the left--you may notice it has a taper at the end. i think this end is inserted last, pushing up against the ohmic contact (dot) that's already plated onto the silicon die. then when it is heated to bond the glass to the dumet, it alloys with the contact.

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how does the dot get there? there's a plating bath that applies an AC voltage that's slightly above the diode's voltage rating. only the good diodes get a dot at the cathode end. bad ones break down and plate on both sides. this means they are heavier...

1 reply 4 retweets 34 likes sort out the bad diodes from the good ones, they dump the whole lot into a very dense fluid. the bad diodes sink, and the good ones float, so they just scrape those off and use them. forget what fluid they use, it's apparently quite toxic. barium something-or-other?

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the sleeves start out with one slug already installed. these all go into special trays. the diode chips are dumped across the tray which is then vibrated at a very specific frequency, causing the diodes to land dot side up!

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(source: friend of mine who used to be involved with diode manufacturing way back in the day)

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cross section of a headphone plug and jack (aka 1/8" or 3.5mm phone plug). you can see the jack has switches in it. these are often used to disconnect an internal speaker.

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annotated version of the headphone plug and jack cross section.

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this is a small audio transformer, but cut in half and polished.

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let's zoom in a bit. now you can see the individual strands of copper!

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cross section of a small audio transformer, zoomed in and annotated.

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here's a 5mm wide surface mount power inductor that's been sanded down to expose the insides!

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and here is the SMD power inductor with annotations. since this is a shielded inductor, it has an outer ferrite shield that helps contain the magnetic field. this reduces the stray magnetic fields which could interfere with other components.

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this is a small PCB-mount magnetic speaker that i've cross sectioned.

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here's the annotated cross section of the PCB-mount magnetic speaker.

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check out this cross section of a bi-color red/green LED! you can see that there are two LED die and two bond wires.

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this is the annotated version of the red/green bi-color LED cross section.

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this is a cross section of a 7-segment LED display. you can see the tiny LED chip!

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annotations calling out the various parts of this cross sectioned 7-segment LED display.

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the LED segment still lights up!

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this is a 3-pin bi-color LED that's been sanded down so you can clearly see the lead frame and LED chips.

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with annotations.

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close-up of the two LED chips. one is shorter than the other.

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cross section of an electret microphone element. 🎤

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annotated cross section of an electret microphone element. 🎤

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you can see the electret film coating on the backplate here. the metallized diaphragm is torn and distorted from the sectioning process

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how it works: the metallized diaphragm and backplate act as the two plates of a parallel plate capacitor. the electret material sits in between, along with a small air gap. the electret gives this capacitor a constant charge, Q...

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...and since the capacitance changes when the diaphragm deflects due to sound coming in because C = e0*A/d, and because Q = CV, the voltage V = (Q/Ae0) * d. in other words, the voltage is directly proportional to the change in distance between the two plates.

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the most fascinating part is the magical electret material. the name is a portmanteau of "electrostatic magnet." it's a material made of polar molecules (positive charge at one end, negative charge at the other) which are all aligned.

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basically you melt the material while it's in a high voltage electric field, causing all the polar molecules to line up, then you let it cool and solidify. now one side is positively charged while the other side is negatively charged. 🧙‍♀️🧲⚡️

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tried a suggestion from and put a little oil on it to clear up the surface a bit. it helped a bit, but now there are tiny bubbles. 😂

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wow, this bi-color LED is even more beautiful from a slightly different angle!

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ever wonder what a 0.1" header and socket look like inside when they're plugged together? wonder no more, rest your eyes on this cross section!

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this is a cross section of a miniature reed relay. they're used by the millions in semiconductor test equipment, then discarded after a million cycles, which happens sooner than you might think!

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this is the annotated cross section of the miniature reed relay. there's a digital cycle counter in the test equipment these are used in, and when that counter passes 1,000,000, the relays are unplugged and thrown out!

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here's what the relay looks like, intact, resting comfortably on George. often a semiconductor test board will have one of these relays per pin, and sometimes more.

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cross section of a PCB-mount slide switch. this one is SPDT. these are quite inexpensive switches!

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here's the annotated cross section of a PCB-mount slide switch. when you push on the actuator, the rocker forces the ball against the spring. the ball rolls over the rocker, applying force to the opposite side, moving the rocker so that it presses up against the opposite contact.

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check out this cross section of a plain old DIP switch. there are 4 switches in this one, and this is one of the switches.

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here's the annotated version of the DIP switch cross section. it's pretty simple! note that the actuator has two detents simply because it's a symmetrical plastic piece that can be installed in either orientation. only one detent is used.

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this is a very cheap pushbutton that i've cut in half so you can see how simple it is inside. please ignore the void in the middle of the spring; i use glue to hold the internal parts in place during sectioning.

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here's the cheap pushbutton switch cross section with annotations.

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ever wonder what a D-sub connector looks like inside? here's a cross section of a DE-9 plug and receptacle.

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naturally i also made an annotated version of this picture so you can tell what's going on. there are a few subtle features of the design, like the tiny little solder dams that prevent solder from wicking up inside the pins and sockets.

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this is a cross section of an electrical component that interacts with you every day! in fact, there's a good chance you've got one very close to you even as you read this. what is it?

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it's a vibration motor! this is the annotated cross section. (there's a little air bubble in the upper right that formed in the glue i used to hold it together for the sectioning process.)

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cross section of a 2N2222 in a TO-18 metal can

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here's the annotated version of the 2N2222 in the TO-18 package. the package is actually pretty complicated! lots of materials science here.

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from this angle you can see the 2N2222 transistor die. 👾

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the transistor lights up like an LED! it happens if you reverse bias the base-emitter junction and trigger an avalanche breakdown (about 10V). h/t for the technique.

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this is a cross section of a quartz crystal in an HC-49 package. ignore the blob of glue on the right, it was to hold the quartz in place during sectioning.

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here's a cross section of a BLOWN LED. why is it so clean? IT CROSS-SECTIONED ITSELF. i have video proof to follow!

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video of an LED failing and cross-sectioning itself right down the middle! 🤯

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annotated version of the LED that failed and cross sectioned itself.

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SMA connectors help move RF signals from place to place. here's an SMA mated connector pair cut in half. they are from two different manufacturers, but fit together perfectly -- tight tolerances are critical for good RF performance!

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annotated cross section of a mated SMA connector pair. this annotation barely scratches the surface because there are a lot of very subtle design features that you'd need a whole class to cover.

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this is a type N connector cut in half. the 'N' stands for Neill, since Paul Neill worked on this connector while at Bell Labs. he also worked on the BNC connector (Bayonet Neill-Concelman).

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this is an annotated cross section of the type N connector. notice the distance between the center conductor and the ground shield changes depending on the dielectric material (air or plastic).

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this is a common BNC plug and jack that have been cut in half. it is quite a complicated and subtle assembly!

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here is the annotated BNC plug and jack cross section. notice that the diameter of the center contact is consistent and only changes when it enters the cable, which is when the dielectric diameter changes as well? this is to maintain a constant 50 ohm impedance.

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it's fascinating to compare the 75 ohm and 50 ohm BNC connectors! the contacts are the same size to prevent damage when accidentally mating 75 ohm to 50 ohm connectors. to keep the 75 ohm impedance, the connector uses an air gap around the wider contacts.

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here's a slightly unusual connector. this is an HDBNC (High Density BNC) connector that's been cross sectioned. it's sometimes used for video broadcast equipment (75 ohms) but this example is 50 ohms. the second image compares it with standard BNC.

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cross section of the HDBNC connector. there are a bunch of air gaps, dielectric thickness changes, and complex features that are telltale signs of computer modeling and simulation.

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this is the cross section of a coaxial cable. it's a LMR-195 cable which is pretty similar to RG-58

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annotated cross section of the LMR-195 cable.

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cross section of a common USB cable.

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annotated cross section of a typical USB cable.

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check out this cross section of an AC power cord. no, the other end is not plugged in.

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here's the cross section of the power cable. this is an older cord with outdated color codes. the filler also appears to be a natural material (possibly jute)

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flat phone cable, in cross section.

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cross section of an old-school VGA cable. i like the color coding. scale is 1mm/div.

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here's the annotated cross section of the VGA cable. each red, green, and blue signal gets its own little coaxial cable, as does the horizontal sync signal. vertical sync is low frequency and noise tolerant, so it's just a wire. same with the DDC signals (SDA, SCL, +5V, GND)

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cross section of a DVI-D single link cable. all that aluminum makes me think it's a cheap cable.

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and the DVI-D single link cable but with annotations.

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closeup of a single differential pair inside the DVI-D single link cable. the geometry has to be tightly controlled to maintain a constant impedance!

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for your inspection: this cross section of a USB-C connector. it's very complex!

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there really isn't enough room for all the annotations you'd need to fully describe this USB-C connector cross section. so here are the highlights.

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ever wonder what's inside your USB-C cable? here's a cross section of one! this one can handle 10Gbps.

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and this is what all the little wires and things are for. SBU stands for "SideBand Use"--DisplayPort alt mode uses them for I2C or CEC commands over a special encoded format. CC is the Configuration Channel and decides VBUS voltage and which end is source/sink.

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this cat6 cable is shielded and has a drain wire.

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and here's a cat6 patch cable! notice the plastic ➕ separator? it reduces crosstalk between pairs.

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and a super-thin cat5e patch cable.

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time to cut some network cables in half! here's a cat5e patch cable. 🐈 (thread)

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this is a cross section of a USB-C cable. it's different than the other USB-C cable that i sectioned earlier!

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annotated USB-C cable cross section. this cable got beat up a bit; one of the micro coax cables has gotten dented or deformed. you can see it's messed with the stranding a bit.

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it's Friday, so take a break from work and look at this: a cross section of a Micro-D connector!

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annotated version of the Micro-D connector cross section.

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