How do you do PCB repair services?
In PCB assembly process Soldering is the process of joining two metal surfaces together with the use of a hot soldering iron, flux, and solder. It's more difficult to remove the same solder if something isn't quite correct. Excessive solder may need to be removed, as with bridging between two contacts, or bad components may need to be removed and replaced in the circuit board repair process.
Solder removal, often known as "desoldering," can be accomplished in a variety of ways:
A copper braid used to absorb solder is known as solder wick, DE soldering wick, or simply "wick." When hot solder is melted, pulled up, and maintained using a combination of wetting and capillary action, it is usually covered with flux. Solder wick allows you to remove solder in discrete places without putting the entire board or neighboring components under heat stress. Because solder wick can only remove solder mask that is accessible, components that cover contact regions, such as ball grid arrays (Bga rework), must be removed before the leftover solder can be removed.
Solder suckers pull molten solder up with a spring-loaded vacuum. Soldering iron or hot air, such as from a heat gun or rework repair station, must be used to melt the solder. Small quantities of solder are pulled up at a time, and removing a component frequently takes numerous efforts. Maintaining soldering temperature or repeatedly remolding a solder junction puts more thermal stress on components, adjacent solder joints, and the circuit board as a whole. Because solder suckers can only extract exposed solder, components covering contact regions, such as ball grid arrays (BGAs), must be removed first before the leftover solder can be removed.
Desoldering stations use a soldering tip with a hole in the center to pull the molten solder up. While rework stations are a particularly effective technique of desoldering, they can only remove exposed solder, therefore components covering contact regions, such as ball grid arrays (BGAs), must be removed first.
Hot air solder stations
These stations use hot air to melt the solder, and the component is then removed using tweezers or a vacuum lifter. Once the component is out of the way, the solder must be removed differently.
Tweezers built of two soldering irons
Imagine gripping the lead regions with a tweezer composed of two soldering irons. The goal is to grip onto the component's leads on both sides to meet all of the soldiers at once. When compared to hot air, this reduces total thermal stress. Once the component is out of the way, the solder must be removed differently.
Using a hot plate to melt (or reflow) all of the solder junctions allows many components to be removed at the same time. Other components and the board as a whole may be overworked as a result of this strategy.
How to use solder wick efficiently?
- Place the braid over the undesirable solder, particularly where there is the most solder build-up, to optimize the braid's contact with the solder's surface area.
- Next, at 45 degrees, set your iron tip over the wick and allow heat to flow to the pad. The braid will absorb the molten solder.
- As needed, adjust the solder tip and braid to remove all of the solders at once. It's important not to drag the braid over the pads since it can scratch them.
- When the braid is full of solder, clip the spent section and switch to a new braid to pull additional solder. To avoid soldering the wire to the board, remove the iron and braid at the same time.
Wide range of available solder wicks?
Solder wick is available in several thicknesses to effectively remove solder from various sorts of contact locations, and it is coated with a choice of fluxes to match your original soldering procedure.
Available sizes of solder wick:
Solder wicks are available in a variety of diameters. Wicks that are too thin will not remove enough solder, requiring you to trim and remelt the solder repeatedly. A wick that is excessively broad may take longer to heat and may interact with other circuit board components.
Select a desoldering wick with a width that nearly matches the contact area. This will guarantee adequate heat conduction and the avoidance of undesirable desoldering. Desoldering wire widths are standardized across the industry and are indicated by the numbers 1 through 6 or by color codes.
• The tiniest braid (under 1mm wide) is used primarily for SMDs and microcircuits.
• The most popular desolder wire colors are #2/yellow, #3/green, and #4/blue.
• For big blobs of solder, use #5/brown, and for desoldering BGA pads or terminals, use #6/red.
• Keep three or four different widths on hand to handle all eventualities.
• To better suit the contact area, the wick can be folded or cut at an angle.
Most used kinds of coating on solder wick:
Rosin – Although rosin-fluxed desoldering wicks have the quickest wicking action, they do leave residues that must be cleaned properly.
No-Clean — When cleaning isn't practicable or possible, a no-clean fluxed desoldering wick is suitable. The only thing left after desoldering is a transparent, non-ionic residue. This is the braid to use in the field when a complete washing is more difficult.
Unfixed - You can add your flux to this type of braid in a production or maintenance environment when the flux is stipulated and cannot be adjusted, or where an aqueous flux is required. If the wick isn't fluxed, it won't be able to remove the solder. Pen packing is offered for many sorts of fluxes, which is suitable for fluxing braid.
Solder wick is also available in various lengths. For usage at a workstation, 5' and 10' lengths are convenient. To avoid harming components susceptible to ESD, static dissipative spools, often known as "bobbins," are offered. Longer spools, such as those measuring 25' (7.6M), 50' (15.2M), 100' (30.5M), and 500' (152.4M), are usually kept in a central place and distributed to technicians as needed.
There are also specific braid patterns available. Chemtronics, for example, provides Solder-Wick Lead-Free, which is designed to heat up quicker and reduce thermal shock in high-heat lead-free applications.
Are you allowed to add your flux to the solder wick?
You can add your flux to this type of braid in a production or maintenance setting when the flux is stipulated and cannot be adjusted, or where an aqueous flux is required. If the wick isn't fluxed, it won't be able to remove the solder. Pen packing is offered for many sorts of fluxes, which is suitable for fluxing braid.
Chemtronics, for example, sells the following flux pens:
No-Clean Flux Pens - This no-clean flux is designed to work at the higher temperatures of lead-free soldering, but it may also be used with tin-lead soldering. To avoid bridging, it is built with low surface tension. Cleaning after soldering is unnecessary since the light residue left behind after soldering is non-corrosive and halide-free. This is a fantastic solution for tin-lead soldering that does not require cleaning.
Rosin Flux Pen - This is a type R rosin flux with a high solid content that provides good solderability in a wide range of applications. The residue left behind is non-corrosive and halide-free, but for aesthetic reasons, it is recommended to remove it after soldering.
Water Soluble Flux Pen - This is a pH-neutral ORH1 flux that is particularly active. It makes both lead-free and lead-containing solders simple to solder. This flux has to be cleaned, and it's simple to do so using DI water in a batch or in-line system, or with Flux-Off Water Soluble Flux Remover on a benchtop.
Tips for perfect, top-notch desoldering.
1. For effective heat conduction, keep your soldering iron tip clean and tinned.
This may sound obvious, but it's often missed, even though it's crucial for effective desoldering. Soldering iron tips that have been contaminated with burned flux and oxidation will not wet (take solder) and will conduct heat inefficiently. A clean and tinned soldering tip distributes heat more efficiently through the desoldering braid and accelerates the wicking process.
2. Reduce the amount of time the board and components are exposed to high temperatures.
High heat levels applied to the board or its components over a long period might damage the board and its components, develop brittle solder junctions, and cause servicing concerns down the road.
Concludingly, Soldering is the technique of using a hot soldering iron, flux, and solder to fuse two metal surfaces. If something isn't quite right, it's more difficult to remove the same solder. Excessive solder, such as bridging between two contacts, may need to be removed, or faulty components may need to be removed and replaced. By reading above, you are now well aware of the techniques and tools for high tech services that are best for Printed circuit board rework services.