Drag soldering works exactly as its name implies, by dragging a bead of solder across fine-pitch pins you can quickly solder an entire row. The method relies on clean joints, so liquid solder flux is often used to make sure there is good flow. But if you’re drag soldering on boards that you’ve etched yourself the solder can sometimes run down the trace, rather than staying where you want it. Professionally manufactured boards don’t have this problem since they have solder mask covering the copper that doesn’t need soldering. [Ahmad Tabbouch] has a method that uses Kapton tape to act as a temporary solder mask on diy boards.
The process involves several steps. First, three strips are place horizontally across the board, leaving just a portion of the upper and lower pads exposed. Those pads are then tinned with solder, and a light touch with an X-acto knife is then used to score the tape covering the vertical rows of pads. Once the waste as been removed, two more strips are added and those rows are tinned. From there the chip is placed and soldered as we’ve seen before; first tacked in place, then fluxed, and finally drag soldered to complete the connections. This achieves a crisp and clean connection, presumably without the need to clean up your solder mess with solder wick.
Kapton tape resists heat, making it perfect for this process. We’ve also seen it used on hot beds for 3D printers, and as a smoothing surface for sliding mechanisms.
[via Dangerous Prototypes]
Hotel room door lock picking
Here’s further proof that you should never leave anything of value in your hotel room. We’re not worried about someone getting in while the room is occupied. But these methods of defeating the chain lock and opening the door without a keycard (YouTube login required) do show how easy it is for the bad guys to steal your stuff.
iPhone frequency generator
Need one more way to make that iPhone a useful lab tool? Why not use it as a frequency generator. Start with a free app and mix in an audio cable with test leads and you’re in business.
[Andrei] sent us a link to a video about drag soldering. This is a method of soldering fine-pitch chips using a small bit of solder and a fat solder tip. The link he sent is dead now but we found another great example of the process. We were just using this method earlier in the week to solder a TSSOP38 package for an upcoming project and it worked like a charm.
Laser etched PCB
Here’s some art in PCB form thanks to a laser. We thought this might be interesting to share after seeing those art pieces made from old circuit boards. This example is laser etched, but not directly. As you probably guessed, the copper clad board is coated with resist and the laser etches some of it away. Whatever got zapped by the laser dissolves when the board is placed in acid, leaving [Riley Porter’s] art behind.