Not all boards will come out perfect the first time they are put through prototyping. In reality, some boards will start to look like Frankenstein after you start testing, desoldering, replacing components, and attaching wires to the PCB. Doing this successfully requires using some basic soldering and rework tools, and it requires the right set of materials and equipment in your lab space.
If you plan to do your own rework on your PCBs, make sure you have the right set of tools to remove components without damaging your board or your other components. If you’re working to kit out your own lab space, take a look at the list below for a complete set of tools you’ll need to rework your PCBs. This list of tools is not comprehensive, but it is a good start for any new designer that wants to build up their rework capabilities.
List of PCB Rework Supplies
First and foremost, you’ll need a set of hand tools so that you can grab parts, cut and strip wires, and lift parts off a board once solder joints are molten. Oftentimes, rework is being performed while testing a prototype and making corrections to various connections in the PCB, so you should keep some of these testing items around as well. The list of hand tools you might need for rework includes:
- Wire cutters
- Wire stripper
- End nippers
- Spare wire leads
- Sleeve wrap for wiring
- Razor blade
- Small drill (either a dremel or a hand drill)
Every engineer and PCB designer should have a basic hand soldering kit. The equipment does not need to be elaborate; most inexpensive soldering kits will contain a soldering iron, holder, some tips, and a thermocouple that can be used with most multimeters. Some soldering kits come with additional pieces, such as additional tips, sponge, or a temperature gauge.
Basic soldering kit from ThinkRobotics.com
There are standalone kits that include power, temperature, wire holder, and iron holder. These kits are not too expensive from an online retailer; you’ll find many options on Amazon or Alibaba.
Wire, Paste, and Flux
Your soldering kit should also include a roll of solder wire (usually tin-lead), solder paste, and a small amount of flux. There are many different varieties of solder wire and solder paste, some which may include lead. There are also fluxes which may require cleaning with alcohol (see below) in order to prevent any tacky or conductive residues on the surface of the PCB. If your soldering kit does not include these items, make sure to purchase these as well as some cleaning supplies.
Isopropyl alcohol is a common cleaner used to remove flux residues, dirt, and contaminants from the circuit board. Lint-free wipes are used to apply the cleaning solution and gently wipe the board without leaving fibers or lint behind. Brushes with soft bristles are helpful for reaching tight spots and cleaning delicate components. These supplies are used by applying isopropyl alcohol to the wipe or brush and then carefully cleaning the circuit board, ensuring it is free from any residues that could affect performance or cause reliability issues.
Desoldering Pump or Solder Wick
These tools are used to remove solder from connections once the solder has been molten with an iron or hot air gun. A desoldering pump (sometimes called a solder sucker) creates a vacuum to suck up the molten solder from component leads; it will then cool and solidify where it can be removed from the desoldering pump. A solder wick (or desoldering braid) can also be used to remove molten solder by absorbing the solder when heated. This is normally used by heating the braid against the solder so that the molten solder can wick directly into the braid.
Solder can be removed easily by applying heat through a solder wick or braid. Image credit: SparkFun Electronics
Soldering pumps can have very large diameter apertures that are not convenient for smaller SMD parts. These pumps can be difficult to fit into tight spaces, so in these instances it is better to use a small soldering iron tip with a solder wick to soak up molten solder and loosen a part. Once most of the solder is removed with a wick, the component can be pulled off with tweezers.
Soldering Fume Extractor
When soldering, some fumes may be emitted that can be harmful to health. This is true for many solder alloys and pastes, including lead-based solder alloys. A fume extractor helps remove these fumes from the work area during rework. If you don’t have room for a fume extractor and you don’t have a fume hood in your lab, you should still consider wearing a mask and providing adequate ventilation in your workspace.
Fume extractors are basically a fan in an enclosure, where air is pulled through a filter. If you’re really feeling innovative, you can try building your own fume extractor with a small power supply, a fan, and a small HVAC air filter in a box.
Clamps and Brackets
A holder or clamp is often needed to hold the position of the PCBA so that heat can be applied to the target components. A set of small clamps and brackets can keep the circuit board in a fixed position or angle during rework. These tools are also useful when soldering wires to component leads or test points.
This type of clamp can hold the PCB at a specific position or angle, which frees up your hands to hold an iron and wire.
The above holder is very basic and it cannot be used to hold, for example, wires or larger mechanical parts that might need to be soldered onto a board. Larger clamps that come with a base and multiple arms are sometimes needed in order to hold larger parts while the operator applies solder with their hands. If you need to free up one of your hands from holding solder wire, consider applying a solder paste and holding your part by hand or with tweezers.
Rework Station: an All-in-One Solution
If money is no object, then you can purchase a high-quality rework station for soldering and desoldering components from a PCB. These stations consolidate all of the above tools into a single set of equipment. Rework stations can also include a microscope and monitor display for clearly visualizing reworked components, a hot air source for melting solder joints, a built-in hot plate, and an iron for hand soldering. These stations can be more expensive, but a skilled operator can get very high-quality results.
SMD rework station from Manncorp.
These rework stations are spendy, and they are the type of platform you’ll find at a manufacturing or assembly facility. If your assembler is performing rework on your PCBA, then they will likely use this kind of rework station. These rework stations typically include clamping, a hot air source, temperature control, exhaust control, and a light source. You’ll notice in the above image that this example station from Manncorp includes a microscope with a CCD camera so that reworked boards can be inspected and verified as you work the board.
There are other rework stations that are much less expensive and do not include all of the options shown in the above image. For example, there are smaller hot air rework stations that do not include clamping or a microscope, but they do provide a convenient temperature-controlled hot air source. A hot air gun is mandatory for removal of any large integrated circuits, including leadless components like BGAs or QFNs.
Hot air rework station from Yihua.
What about BGA rework? The above solder rework stations options will allow you to remove a BGA package from a PCBA, but the removal of a BGA will result in a mess of molten solder on the bottom side of the BGA package. There will also be solder leftover on the PCB in the BGA land pattern. After cleaning up the landing pads on the PCB with some flux and a solder braid/desoldering pump, the area can have a new BGA installed or the BGA itself can be reworked.
BGA Reballing and Resoldering
Reworking (or reballing) a BGA requires a soldering station with a heating platform. These stations include a hot air source station and a heating platform. The hot air rework station applies controlled heat to melt the leftover solder on the bottom side of the BGA package so that it can be removed. Next, the BGA package is placed on the heating platform and a stencil with an array of small apertures corresponding to the solder ball positions is aligned over the package. Balls of solder alloy are then placed through the stencil and these bond to the exposed pads on the bottom side of the package.
Next, the BGA can be reattached to the PCB using a heating platform. The heating platform elevates the temperature of the entire board, and a hot air gun is then used to apply targeted heat to the BGA package so that the solder balls can melt onto the landing pads. One of the challenges here is to ensure heat is only applied to the BGA during rework such that other components do not become desoldered. This may require adjusting the hot air gun nozzle size and airflow to prevent other components from being damaged.
No matter what components you need to mount or rework on your PCBA, you can design for success with the complete set of industry-standard PCB design features in OrCAD from Cadence. Only Cadence offers a comprehensive set of circuit, IC, and PCB design tools for any application and any level of complexity.