Remove the solder, then the iron, while keeping the joint still. Allow the joint a few seconds to cool before you move the circuit board. Inspect the joint closely. It should look shiny and have a 'volcano' shape. If not, you will need to reheat it and feed in a little more solder. This time ensure that both the lead and track are heated fully before applying solder.
Some components, such as transistors, can be damaged by heat when soldering so if you are not an expert it is wise to use a heat sink clipped to the lead between the joint and the component body. You can buy a special tool, but a standard crocodile clip without a plastic cover works just as well and is cheaper. The heat sink works by taking some of the heat being supplied by the soldering iron and this helps to prevent the component's temperature increasing too much.
Rapid Electronics: crocodile clip. It is very tempting to start soldering components onto the circuit board straight away, but please take time to identify all the parts first.
Sticking them onto a sheet of scrap paper and labelling each one is worthwhile and you are less likely to make a mistake if you do this. Some ICs are static sensitive and will be supplied in antistatic packaging - leave these ICs in their packaging until you need them, then earth your hands by touching a metal water pipe or window frame before handling the ICs.
Many must be placed the correct way round and a few can be easily damaged by the heat from soldering. The table shows advice for the various components and a suggested order to put them on the board.
Generally it is best to start with the smallest parts but for stripboard it is helpful to start with the IC holder s as a reference point for other parts. Wire links between points on the board can be made with plastic-coated single core wire which will need stripping, or tinned copper wire if the link won't touch other parts.
Tinned copper wire looks just like solder but you can feel the difference, it is stiffer than solder and it won't melt. Single core wire is unsuitable because it snaps when repeatedly flexed. Modern lead-free solder is an alloy of tin with other metals including copper and silver.
Always wash your hands after using solder , this is especially important with traditional solder because it contains lead which is toxic. Rapid Electronics: lead-free solder. Solder for electronics use contains tiny cores of flux, like the wires inside a mains flex.
The flux is corrosive, like an acid, and it cleans the metal surfaces as the solder melts. This is why you must melt the solder actually on the joint, not on the iron tip. Without flux most joints would fail because metals quickly oxidise and the solder itself will not flow properly onto a dirty, oxidised, metal surface.
At some stage you will probably need to desolder a joint to remove or re-position a wire or component. There are two ways to remove the solder:. Also known as a 'solder sucker'. It is best to use one with an ESD electrostatic discharge nozzle to protect some ICs which can be damaged by static electricity. Rapid Electronics: desolder pump. The copper braid acts as a wick for the molten solder which readily flows onto the braid, away from the joint.
Rapid Electronics: desolder braid. After removing most of the solder from the joint s you may be able to remove the wire or component lead straight away allow a few seconds for it to cool. If the joint will not come apart easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling the joint apart, taking care to avoid burning yourself. Rapid Electronics have kindly allowed me to use their images on this website and I am very grateful for their support.
They stock a wide range of components, tools and materials for electronics and I am happy to recommend them as a supplier.
First a few safety precautions: Never touch the element or tip of the soldering iron. If you burn yourself see First Aid for Burns. If you burn yourself see First Aid for Burns below. Terminations can be classified into two general categories: 1 older thick film silver or silver-palladium 80AgPd metallizations and 2 the more popular barrier type termination used for surface mount components. The silver-palladium termination has adequate resistance to solder leach and less tendency to tarnish than pure silver terminations.
Silver finds application mostly on units destined for axial or radial leading or on specialty items, such as high voltage capacitors which require the use of more ductile silver metal to reduce thermal shock hazards to these units when leaded.
Silver bearing terminations can tarnish. Usually packed with a tarnish retardant paper, capacitors will store indefinitely and solder properly with the appropriate fluxes. Note that product supplied in reeled format cannot be effectively protected by tarnish retardant paper, as units stored in bulk; hence, inventory planning or the use of barrier termination is recommended. Barrier layer terminations are based on plating technology to provide to microinches of nickel thickness over a fired silver termination.
The electrolytic process is perhaps the preferred method of nickel deposition. A current is utilized to deposit nickel from nickel sulfamate and nickel chloride in a boric acid solution onto the silver termination of the capacitor. This termination differs from conventional materials in that the frit which bonds the termination to the capacitor must be chemically resistant to the plating solutions and thus is bismuth free.
Such frits do not promote solderability; hence, units with this termination are unsolderable unless properly plated with nickel and solder. Immediately after the nickel process, units must undergo the solder process before the onset of any oxidation of the base metal layer. Units are electroplated using tin and lead concentrates in a deionized water solution.
An electroless method of nickel deposition, based on chemical reduction of nickel boron solutions and catalytic activators, can also provide a continuous nickel barrier layer, but this is not as suitable for tin lead plating. Alternate application of a solder coat by wave soldering methods creates dimensional tolerance difficulties, which is not desirable for components to be taped and reeled for use in surface mount technology. The distinct advantage of the nickel barrier termination is evident in its name; it serves not only as a guard against solder leach, by virtue of the relatively insoluble nature of nickel in solder alloys, but also forms a barrier to the formation of intermetallic compounds in the solder joint which can adversely affect the long term reliability of the bond.
Non-barrier terminations can be affected by a time-dependent diffusion phenomenon of Ag, Pd and Sn atoms, which accelerate with thermal cycling and can eventually lead to stress cracks separating the component from the assembly. Capacitors with nickel barrier terminations have been shown to arrest the diffusion process and the formation of intermetallic compounds, hence maintaining the integrity of the bond.
Although it is a characteristic of all nickel deposition to retain a contractile or tensile condition, the industry has developed the methods to plate the material with controlled metallographic structure and ductility to produce physical and mechanical properties suitable for all the dielectric types of multilayer capacitors.
Chip terminations and bonding alloys contain metals notably silver and tin , which can hydrolyze in the presence of water moisture. Under the influence of an electric field, the hydroxide can dissociate to form metal cations, which have a net positive charge and can migrate to the cathode.
This phenomenon occurs with AC voltage as well as with a DC bias, and the severity is directly proportional to the voltage gradient.
Given enough time, a bridge of silver or tin will form between chip terminations, reducing the insulation resistance and eventually forming an electrical short. Avoidance of this problem can be accomplished with the use of very expensive gold terminations and substrate conductors or with the elimination of water moisture from the circuit, which precludes the formation of mobile cations. The latter is accomplished by hermetic sealing of circuits or the use of waterproof encapsulants such as epoxies.
Hopefully, Part 13 gave you a better understanding of soldering and chip termination guidelines and how these best practices may affect your specific application. Also, check out our Knowles Precision Devices Capacitors to view our complete product offering. Topics: Capacitor. Knowles Precision Devices Blog. Chip Capacitor Attachment Methods Chip bonding to substrates can be categorized into two general classes: 1 methods involving solder and 2 those involving other bonds, such as epoxies and wire bonds thermal-compression and ultrasonic bonding.
Surface mount components are attached to the substrate by pick and place machines, and held in place by epoxy or solder paste for subsequent processing, which may involve any of the following: Infrared IR Solder Reflow : This method was briefly described above and has the advantage of having precise temperature profiles. This allows for good control of the many parameters of the circuit assembly, including volatilization of solvents, activation of fluxes, solder reflow and wetting time, and uniform and gradual cooling.
IR Heat Transfer: This method is by direct radiation, and different, specific profiles need to be established for variations in board type and configuration. Vapor Phase Reflow: This method is based on rapid and thermally efficient transfer of heat from hot vapors to the hybrid assembly.
The advantage of this system is that total immersion of the circuit in the hot vapor provides a more uniform heat transfer for reflowing the solder. However, problems may arise with sudden outgassing of paste constituents and thermal shocking of components. A capacitor was already removed from the two solder pads. Each pad was heated while the capacitor was pulled away from the board. Notice how the solder holes are completely covered with solder.
Opening these holes -- so the capacitor lead can be pushed through -- will greatly simplify installation. To open the hole blocked by solder, heat the solder pad with the tip of a soldering iron.
Push through the molten solder from the other side with a staple or sewing needle. In our case, we decided to use a right angle pick. Lead solder will not stick to steel, so pretty much any thin steel can be used. Pushing the tool all the way through the hole may require heating the pad several times. As a rule of thumb, heat the solder just enough for it to melt, then remove the soldering tip from the pad.
Excessive heat will damage electronic components. When the tool has completely passed through the hole, enlarge the hole by heating the top side of the solder pad while pressing through with the tool. Both solder holes should now be open enough to insert the bare leads of your component.
Prepare your component for soldering by removing any excess solder from the contacts. The contacts should be clean enough to pass through the solder pad holes. Run the soldering iron tip down the lengths of each contact to wipe the solder away from the component. Clean the iron's tip between strokes by wiping it against a moist sponge.
Excessive heat will damage the components, so do not apply the soldering iron to the component for long amounts of time. To ease in soldering, slightly bend the contacts protruding through the holes so they hold themselves in place. Melt just enough solder onto the solder pad so that the capacitor's contact lead holds firmly in place. Remove both the solder and the soldering iron tip from the connection as soon as enough solder melts onto the pad.
Next we will cover a moderately difficult soldering application. In our case, we will be soldering very thin and delicate leads to a circuit board with small solder pads. Small electronic components, including wires, cannot dissipate heat as quickly as larger components.
This makes them very susceptible to overheating. Make sure to heat the connection just long enough to melt the solder. The leads were removed from the solder pads by heating the joint on the top side of the board, while pulling out the leads with a pair of tweezers. It is common for solder to cover up some of the holes through solder pads on the board. Opening these holes greatly simplifies soldering.
Open the holes through the solder pads by pressing a straightened staple against the blockage while heating the same pad from the other side of the board. A " third hand " tool or a friend can greatly help in this procedure.
After clearing all of the holes, insert the bare ends of the leads with a pair of tweezers. To keep the leads in place, it may be helpful to first bend the battery leads into their final shape, then insert the stripped ends into the holes. Melt just enough solder onto the solder pad so that the contact leads hold firmly in place.
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