BGA Hand Soldering Uses Tombstone Resistor Technique, Demands Surgical Precision

Most Hackaday readers will be a pretty dab hand with a soldering iron. We can assemble surface-mount boards, SOICs and TSSOPs are a doddle, 0402s we take in our stride, and we laugh in the face of 0201s. But a Twitter thread from [Greg Davill] will probably leave all but the most hardcore proponents of the art floundering, as he hand-wires a tiny FPGA in a BGA package to the back of a miniature dot-matrix LED display module.

Resistors soldered on-end, awaiting wires to connect to the BGA microcontroller

As far as we can see the module must once have had its own microcontroller which has been removed. We’d guess it was under an epoxy blob but can’t be sure, meanwhile its pads are left exposed. The Lattice LP1k49 fits neatly into the space, but a web of tiny wires are required to connect it to those pads. First, [Greg] populates the pads with a set of “tombstoned” tiny (we’re guessing 0R) resistors, then wires them to the pads with 30μm wire. He describes a moment of confusion as he attempts to tin a stray hair, which burns rather than accepting the solder.

The result is a working display with a new brain, which surprises even him. We’ve seen more than one BGA wiring over the years, but rarely anything at this scale.

It’s worth mentioning that [Greg] was behind the FLIR frame grabber that was a runner-up in last year’s Hackaday Prize. We admire the photos he’s able to get of all of his projects and aspire to reach this level with our own. Take this as inspiration and then check out the Hackaday contest for Beautiful Hardware images happening right now.

Thanks [Sophi] for the tip.

Homemade Magic Makes The Metcal Go

First soldering irons are often of the Radioshack or Maplin firestarter variety. They’re basically wall power shorted across a nichrome heater or similar with some inline resistance to make it harder to burn down the house. You plug them in, the current flows, and they get hot. Done.

If you stick with the hobby for a while, these eventually get replaced with something like the venerable HAKKO FX-888D or that one Weller everyone likes with the analog knob. These are much improved; having temperature control leads to a more consistently heated tip and much improved soldering experience.

Entering the electronics workplace one comes across the next level of quality soldering iron: high end HAKKOs, Metcals, JBCs, and the like. Using one of these irons is practically a religious experience; they heat in a flash and solder melts while you blink. They even turn off when you put the handpiece down! But they’re expensive to buy (hint: think used). What’s a hobbyist to do?

[SergeyMax] seems to have had this problem. He bit the bullet, figured out how the Metcal works, and made his own base. This is no mean feat as a Metcal might look like a regular iron but it’s significantly more complex than ye olde firestarter. The Metcal magic is based on a oscillating magnetic fields (notice the handpiece is connected via BNC?) interacting with a tip bearing a special coating. In the presence of the changing field the tip heats up until it hits its Curie temperature, at which point it stops interacting with the magnetic field and thus stops heating.

When the user solders, the tip cools by sinking its heat into the part and drops below the Curie temperature again, which starts the heating again. It’s like temperature control with the sensor placed absolutely as close to the part as possible and a nearly instant response time, without even a control loop! [SergeyMax] has a much more thorough description of how these irons work, which we definitely recommend reading.

So what’s the hack? Based on old schematics and some clever reverse engineering from photos [SergeyMax] built a new base station! The published schematic is as rich with capacitors and inductors as one could hope. He didn’t post source or fab files but we suspect the schematic and photos of the bare board combined with some tinkering are enough for the enterprising hacker to replicate.

The post contains a very thorough description of the reverse engineering process and related concerns in designing a cost efficient version of the RF circuitry. Hopefully this isn’t the last Metcal replacement build we see! Video “walkthrough” after the break.

Edit: I may have missed it, but eagle eyed commentor [Florian Maunier] noticed that [SergeyMax] posted the sources to this hack on GitHub!

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Solder SMDs With A Pan O’ Sand

For those that grew up working with through-hole components, surface mount parts can be challenging to deal with. However, there are plenty of techniques out there that are more than accessible to the DIY set. With the right gear, soldering SMD boards is a snap – just get yourself a hot pan of sand (Youtube link, embedded below)!

The process starts with a professionally manufactured PCB, and accompanying stencil. All major PCB CAD packages are capable of generating stencil files these days, and many manufacturers will throw in a laser cut stencil for minimal extra cost with a PCB order. The board is first mounted on a stable surface, and has solder paste applied, before components are placed with tweezers. Perfect placement isn’t necessary, as the surface tension of the molten solder pulls components into their correct orientations. The populated board is then placed on a bed of sand in a frying pan, which is placed on an induction cooktop. The board is then heated until the solder melts, and all the components are neatly reflowed. Once allowed to cool, the board is done!

The trick is that the sand helps evenly heat the circuit board, while keeping it a safe distance away from the heat source. Results are good, and the process is far quicker than hand soldering. It’s easy to keep an eye on the process too. Of course, the traditional method is still to use the humble toaster oven, but new techniques are always useful. We’ve seen it done with a Bunsen burner, too. Video after the break.

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The Fascinating World Of Solder Alloys And Metallurgy

Solder is the conductive metal glue that one uses to stick components together. If you get the component and the PCB hot enough, and melt a little solder in the joint, it will stay put and conduct reliably. But it’s far from simple.

There are many different solder alloys, and even the tip of the soldering iron itself is a multi-material masterpiece. In this article, we’ll take a look at the metallurgy behind soldering, and you’ll see why soldering tip maintenance, and regular replacement, is a good idea. Naturally, we’ll also touch upon the role that lead plays in solder alloys, and what the effect is of replacing it with other metals when going lead-free. What are you soldering with? Continue reading “The Fascinating World Of Solder Alloys And Metallurgy”

Hackaday Podcast Ep18: Faxploitation! Ikea RFID Hacking, Space Ads, Hydrogen Dones, And Blinkies

Hackaday editors Elliot Williams and Mike Szczys gather round the microphone to spin tales from a week of hacks. All the rage are fax-machine-based malware, a hydrogen fuel cell drone, and bringing color to the monochrome world of the original Super Mario Land. There are at least three really cool LED hacks this week, plus Tom’s been exploring space advertising, Maya’s debunking solder myths, and Elliot goes ga-ga for a deep Ikea electronics hack. Closing out the show is an interview with Bart Dring about his exquisitely-engineered string art robot.

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Direct download (68 MB of audio splendor)

Places to follow Hackaday podcasts:

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Get To Know The Physics Behind Soldering And The Packaging Of ICs

Often it feels as if soldering is deemed to be more of an art form than something that’s underpinned by the cold, hard reality of physics and chemistry. From organic chemistry with rosin, to the material properties of fragile gold bond wires and silicon dies inside IC packages and the effects of thermal stress on the different parts of an IC package, it’s a complicated topic that deserves a lot more attention than it usually gets.

A casual inquiry around one’s friends, acquaintances, colleagues and perfect strangers on the internet usually reveals the same pattern: people have picked up a soldering iron at some point, and either figured out what seemed to work through trial and error, or learned from someone else who has learned what seemed to work through trial and error. Can we say something scientific about soldering?

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3D Printer Becomes Soldering Robot

What do you do if you have to solder thousands of through-hole parts? The expensive, professional way of doing this is running the boards through a wave soldering machine, or a machine with a fancy CNC solder fountain. The amateur way of soldering thousands of through-hole joints is putting some boards on the workbench and sitting down with a soldering iron. There is nothing in between; you’re either going to go with full automation for a large soldering job, or you’re doing it completely manually. That’s the problem this soldering robot solves. It’s a small, cheap, but still relatively capable soldering robot built out of a 3D printer.

This project is a solution to the development hell of the OpenScan project. This project is built around a small, simple printed circuit board that uses several 0.1″ female headers to connect an Arduino and motor drivers. Soldering them by hand is simply boring, and 3D printers are cheap, so the great mind behind this project decided to use a printer to pump out solder.

The modifications to the printer include a mount for a TS100 soldering iron and a modified filament extruder that pushes a spool of solder through a PTFE tube. The GCode for this soldering job was created manually, but you could also use a slicer instead. After 20 hours of development, the ‘success rate’ – however that is defined – is between 60-80%. That needs to get up to four or five nines before this DIY soldering robot is practical but this is a decidedly not-bad result for a few hours of tinkering.

This printer mod works great for the use case of stuffing a few 0.1″ headers into a board and letting a robot automatically solder the joints, but this printer will run into a problem with the general case of soldering a lot of randomly-shaped through hole parts. You need to actually hold the parts up against the board while soldering. There’s an easy solution to this problem: just flip the 3D printer upside down. This hack of a cheap 3D printer is so, so close to being a great solution to soldering thousands of through-hole parts quickly and easily, and we’re looking forward to seeing where the community takes this idea. You can check out the video demo below.

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