A Christmas Wishlist for At-Home Engineers
The world has changed. More engineers are working from home than ever before and many are tasked with solving problems they would have previously done in a lab. One such problem is how to rework a board at home.
Rework is the process of correcting mistakes or repairing damaged components on a printed circuit board. Sometimes engineers choose the wrong components, or perhaps inadvertently short out a component during probing. How the problem happens isn’t important, but how to fix the problem is. If you’ve damaged an FPGA, you’ll need to send your board to your assembly house for repair. But if you need to adjust the frequency of a pi-filter, you can likely do that at home in a few minutes.
You’ll need some basic tools for the job — a printed circuit board holder, magnification, heat, manipulators, and fresh solder.
The first thing you need is a device to hold your board in place while you work on it. You can use almost anything as long as it is stable, secure, and ESD safe. Stay away from Loc-Line for the board holder (although it’s perfect for positioning probes and alligator clips). Several commercial options are available from companies such as Panavise, Stickvise, Bernsten, etc…
Printed Circuit Board Holder Options
This PCB Circuit Holder includes a steel base with six spring-loaded magnetic posts. It can grab the PCB from the edges or slip inside mounting holes.
Toolour 6 piece PCB Circuit Holder image courtesy Amazon.com
Another option uses a large weight and a gentle screw clamp to grab a PCB from the side — provided you have a large enough setback from the sides.
Or if you are a bit more of a traditionalist, Panavise’s PCB holders have been around for decades.
Panavise 333 Rapid Assembly Circuit Board Holder. Image courtesy Amazon.com
If you work with smaller boards, and need something that can fit easily on your desk without taking up too much space, you might consider the stickvise. And what’s more, the creator posts the information and plans to build your own at the stickvise homepage.
And there’s something to be said for just dropping your PCB right on a worksurface. Silicone mats provide an ESD safe and slip-free work area for your projects.
Now that your work is fixed in place, you’ll need a way to see it.
You need some way to see what you are working on while you are working on it. That means you need a working distance of at least several inches. Inexpensive inspection devices such as this USB microscope don’t really fit the bill since they have to almost touch the board to be useful and it is very difficult to fit a soldering iron between the plastic ring and the microscope. Additionally, the stand is difficult to precisely position.
USB Inspection Microscope from amazon.com
Spending a little more money gets you essentially the same microscope with a rack-and-pinion adjustable focus, an LCD screen, and additional lighting.
This 7” LCD adds a nice touch to a 1200x magnification microscope. Image courtesy Amazon.com
The primary issue with these types of microscopes is that the magnification is fixed, the dial simply adjusts the focus.
To take the next step in home magnification options, investigate Amscope binocular and trinocular microscopes. These inexpensive scopes start at around $300 and have adjustments for focus and zoom. You should note that as zoom increases, the lighting decreases. You might need to purchase an external illumination ring since ambient lighting will likely not be sufficient.
Amscope double-arm boom stand microscope is pictured with external illumination and a digital camera. Image from amazon.com
You’ve got to get solder to a particular temperature to allow it to enter its liquid phase. And the goal is to get it to just barely the necessary temperature without going to much hotter. For that you’ll need a rework station of some sort. That might be a simple soldering iron, or that might be an IR heat source with preheater zones and a hot-air blower.
The costs have really come down in recent years and you can purchase the devices individually or combined into complete packages. This particular rework station sports a soldering iron, a preheating hot plate, an IR heat source and a hot-air gun.
Image of YIHUA 1000B- 4 in 1 Station from Amazon.com
You can also purchase (or make your own) reflow oven inexpensively enough.
This infrared oven image is from amazon.com
But first you have to place your parts on the board.
SMT Tweezers either grab and hold components through friction or through suction. Friction-held tweezers. Friction held tweezers usually have stainless steel tips. However, you can purchase plastic-tipped or ceramic tipped tweezers as well. And if you don’t like the tips they send you, you can always 3D print your own.
These reverse ceramic tipped tweezers require you to squeeze to release the component. Image from Amazon.com
You can also experiment with vacuum pickup tools.
Image of inexpensive vacuum pen device from Amazon.com
At-home rework can be incredibly frustrating and time-consuming. It’s often better to let professionals with the right equipment (and the right inspection equipment) do it for you. But if you’re back is up against the wall this Christmas, and you don’t have any non-leaded parts, you might just give it a go yourself with these inexpensive tools.
Do yourself a favor though, and use fresh solder-paste. The stuff sitting on your desk has likely exceeded its working life.
Merry Christmas from all of us at Advanced Assembly!