 |
 |
|
|
TW International Limited TW House, Oxford Road, Calne, SN11 8RS, UK Next day delivery on most products
Telephone:
44 (0) 1249 822100 / 821818 Click Here To Enter Site
For Direct deliveries in mainland China Hong Kong e-mail us on twltd@yahoo.cn 中国,辽宁省,抚顺市顺城区,11 方块,顺城职专教师公寓,5 号楼,2 单元,101 室. 113006 We supply CAT1010 MANUFACTURED AND EEC + USA APPROVED METERS, Screen Printed labels and Printed Catalogues To Your Specifications direct from China factory WORLDWIDE to volume users saving you money on quality products send us an e-mail with your requirement and we will quote for goods delivered to your factory E-MAIL US ON twltd@yahoo.cn
|
   
|
| Online Products List UK and Exports
LINKS TO OUR PARTNERS
FluxIn high-temperature metal joining processes (welding, brazing and soldering), the primary purpose of flux is to prevent oxidation of the base and filler materials. Tin-lead solder (e.g.) attaches very well to copper, but poorly to the various oxides of copper, which form quickly at soldering temperatures. Flux is a substance which is nearly inert at room temperature, but which becomes strongly reducing at elevated temperatures, preventing the formation of metal oxides. Secondarily, flux acts as a wetting agent in soldering and brazing processes. A flux must be properly selected for the process; a soldering flux will vaporize and have no effect at the high temperatures used for welding. For hand soldering operations, 'flux-core' solder is often used. The solder is formed into a small tube, with a liquid flux in the centre. Flux is automatically delivered in the appropriate quantity as the solder is used. Similarly, brazing rods are usually available with a coating of solid flux. Traditionally, soldering fluxes have required post-process removal due to their chemical activity, which would eventually erode the base material and result in an unreliable connection. This required the use of alcohol or other volatile solvents, which typically resulted in pollution of the air and/or the environment. Fluxes currently available include water-soluble fluxes (no VOC's required for removal) and 'no-clean' fluxes which are mild enough to not require removal at all. Performance of the flux needs to be carefully evaluated -- a very mild 'no-clean' flux might be perfectly acceptable for production equipment, but not give adequate performance for a poorly-controlled hand-soldering operation. In some modern processes, an inert gaseous environment is used which doesn't support oxidation. These processes can obviate the need for flux.
Basic electronic soldering techniques A tube of TW
solder electronics solder used
for manual soldering
All solder pads and device terminals must be clean for good wetting and heat transfer. The soldering iron or gun must be clean and pre tinned with solder, otherwise components may heat up excessively due to poor heat transfer. The devices must then be mounted on the circuit board properly. One technique is to elevate the components from the board surface (a few millimetres) to prevent heating of the circuit board during circuit operation. After device insertion, the excess leads can be cut leaving only a length equal to the radius of the pad. You may use plastic mounting clips or holders for large devices to reduce mounting stresses. Heat sink the leads of sensitive devices to prevent heat damage. Apply soldering iron or gun to both terminal lead and copper pad to equally heat both. Apply solder to both lead and pad but never directly to the tip of soldering iron or gun. Direct contact will cause the molten solder to flow over the gun and not over the joint. The moment the solder melts and begins to flow, remove the solder supply immediately. Do not remove the iron yet. The remaining solder will then flow over the junction of the lead and pad, assuming both are free of dirt. Let the iron heat the junction until the solder flows and then remove the iron tip. This will ensure a good solid junction. Remove the iron from the junction and let the junction cool. Solder flux will remain and should be removed. Be sure not to move the joint while it is cooling. Doing so will result in a fractured joint. Do not blow air onto the joint while it is cooling; Instead, let it cool naturally, which will occur fairly rapidly. A good solder joint is smooth and shiny. The lead outline should be clearly visible. Clean the soldering iron tip before you begin on a new joint. It is absolutely important that the iron tip be free of residual flux. Excess solder should be removed from the tip. This solder on the tip is known as keeping the tip tinned. It aids in heat transfer to the joint. After finishing all of the joints, remove excess flux residue from the board using alcohol, acetone, or other organic solvents. Individual joints can be cleaned mechanically. The flux film fractures easily with a small pick and can be blown away with canned air. In solder formulations with water-soluble fluxes, sometimes pressurized carbon dioxide or distilled water are used to remove flux. Traditional solder for electronic joints is a 60/40 Tin/Lead mixture with a rosin based flux that requires solvents to clean the boards of flux. Environmental legislation in many countries, and the whole of the European Community area, have led to a change in formulation. Water soluble non-rosin based fluxes have been increasingly used since the 1980's so that soldered boards can be cleaned with water or water based cleaners. This eliminates hazardous solvents from the production environment, and effluent.
Desoldering and ResolderingDue to the dissolution of the base metals into the solder, solder should never be reused; once the solder's capacity to dissolve base metal has been achieved, the solder will not properly bond with the base metal and a cold solder joint with a hard and brittle crystalline appearance will usually be the result. It is good practice to remove solder from a joint prior to resoldering - desoldering wicks or vacuum desoldering equipment can be used. Desoldering wicks contain plenty of flux that will lift the contamination from the copper trace and any device leads that are present. This will leave a bright, shiny, clean junction to be resoldered. The lower melting point of solder means it can be melted away from the base metal, leaving it mostly intact though the outer layer will be "tinned" with solder. Flux will remain which can easily be removed by abrasive or chemical processes. This tinned layer will allow solder to flow into a new joint, resulting in a new joint, as well as making the new solder flow very quickly and easily.
Lead-free Electronic SolderingMore recently environmental legislation has specifically targeted the wide use of lead in the electronics industry. The ROHS directives in Europe require many new electronic circuit boards to be lead free by 1st July 2006, mostly in the consumer goods industry, but in some others as well. Many new technical challenges have arisen with this endeavour. For instance, traditional lead-free solders have a significantly higher melting point than lead-based solders, which renders them unsuitable for use with heat-sensitive electronic components and their plastic packaging. To overcome this problem, solder alloys with a high silver content and no lead have been developed with a melting point slightly lower than traditional solders. Lead-free construction has also extended to components, pins, and connectors. Most of these pins used copper frames, and either lead, tin, gold or other finishes. Tin finishes are the most popular of lead-free finishes. Nevertheless, this brings up the issue of how to deal with tin whiskers. Somehow, the current movement brings the electronics industry back to the problems solved in the 1960s by adding lead.jedec has created a classification system to help lead-free electronic manufacturers decide what kind of provisions they want to take against whiskers, depending upon their application creaticity.
Stained Glass SolderingHistorically soldering tips were copper, placed in braziers. One tip was used; when the heat had transferred from the tip to the solder (and depleted the heat reserve) it was placed back in the brazier of charcoal and the next tip was used. Currently, electric soldering irons are used; they consist of coil or ceramic heating elements, which retain heat differently, and warm up the mass differently, internal or external rheostats, and different power ratings - which change how long a bead can be run. Common solders for stained glass are mixtures of tin and lead, respectively:
Pipe/Mechanical solderingSometimes it is necessary to use solders of different melting points in complex jobs, to avoid melting an existing joint while a new joint is made. Copper pipes used for drinking water should be soldered with a lead-free solder, which often contains silver. Leaded solder is not allowed for most new construction, though it is easier to create a solid joint with that type of solder. The immediate risks of leaded solder are minimal, since minerals in municipal or well water supplies almost immediately coat the inside of the pipe, but lead will eventually find its way into the environment. Tools required for pipe soldering include a blowtorch (typically propane), wire brushes, a suitable solder alloy and an acid paste flux, typically based on zinc chloride. Such fluxes should never be used on electronics or with electronics tools, since they will cause corrosion of the delicate electronic part.
Soldering defectsSoldering defects are solder joints that are not soldered correctly. These defects may arise when solder temperature is too low. When the base metals are too cold, the solder will not flow and will "ball up", without creating the metallurgial bond. An incorrect solder type (for example, electronics solder for mechanical joints or vice versa) will lead to a weak joint. An incorrect or missing flux can corrode the metals in the joint. Without flux the joint may not be clean. A dirty or contaminated joint leads to a weak bond. A lack of solder on a joint will make the joint fail. An excess of solder can create a "solder bridge" which is a short circuit. Movement of metals being soldered before the solder has cooled will make the solder appear grainy and may cause a weakened joint. Soldering defects in electronics can lead to short circuits, high resistance in the joint, intermittent connections, components overheating, and damaged circuit boards. Flux left around integrated circuits' leads will lead to inter-lead leakage. It is a big issue on surface mount components and causes improper device operation as moisture absorption rises, In mechanical joints defects lead to joint failure and corrosion. FOR SOLDERING STATION PDFs CLICK HERE Copyright Notice TW GROUP MAKES NO GUARANTEE OF VALIDITY CONTENT WORLD COPYRIGHT RESERVED © 2005 R WHEELER TW INTERNATIONAL GRP LTD TW HOUSE OXFORD ROAD CALNE SN11 8RS UK TW have provided this document as a free web resource to help constructors, trainees and students. You are welcome to download it, print it and distribute it for personal or educational use. It may not be used in any commercial publication, mirrored on any commercial site nor may it be appended to or amended, or used or distributed for any commercial reason, without the prior permission of TW International Ltd. Every care has been taken to ensure that the information and guidance given is accurate and reliable, but since conditions of use are beyond our control no legal liability or consequential claims will be accepted for any errors herein. The British mains voltage supply is 230V ac and you should amend ratings for local conditions.
|
|
|
We
supply Weller Soldering, TW Meters, Fluke Meters, Avo, TW Hand Tools,
Sumitomo Heat shrink Tubing, Erem Tools, Erop Tools, Tweezers, Antistatic
wrist bands, coil cords, Silicone tube, Cushion handle coverings, rig
tubing's, King Dick tools, Elora tools, Draper tools, Sthalwille tools,
Wiha, Wera, C Spanners, Labels and identification, heat shrink printed
identification markers, 3m markers and scotch tapes, Toray, ceramic
adjusters, in fact we can supply you with all the equipment needed
to run a factory (ISO 9001:2000 REGISTERED COMPANY AND SUPPLIERS TO
ROCKET DIVISION OF NATO)
Registered
company with the department of FAIR TRADING (Reg. No. 2600896) and official
credit brokers so feel SAFE in dealing with a
trusted
company.
Account
customers can purchase goods by using their unique account number, and
re-sale shops can visit our special RE-SELLERS SITE (twproducts.co.uk)
All other customers can purchase goods using Visa/Delta or MasterCard
or cheque/bank transfer
Fishing Shop TW Tackle Direct 10 Belgrade Promenade Ilfracombe Devon EX34 9AS 01271 862363E-MAIL fish@tackledirect.co.uk Tackle Direct Oxford Road Calne Wiltshire 01249 821818E-MAIL sales@tackledirect.co.uk TW Jewellery Shop TW Conningtons 35 High Street Ilfracombe Devon EX34 9DA 44 (0) 1271 865349 E-Mail twring@tiscali.co.uk Consumer product links Products from the above outlets are also offered to our industrial customers at discounted prices please use your account number to claim your discounts.
At TW we pride ourselves in giving our customers a first class service and a comprehensive products range from Weller Soldering stations, De Soldering Stations, Heat Shrink Tubing, Soldering Irons, Spanners, Socket Sets, Fluke Meters, Multi Meters, Avo Multi Meters, Tool Cases, Platt Cases, Tool Kits, WD1000, WSD81, WS81, TCP Soldering Irons, WTCP51 Soldering Station, WMD1 Re Work Station, WSD161V Re Work Soldering Station, Conduit Bending Springs, Electrical Labels, Danger Labels, Electric Screwdrivers, Hios Screwdrivers, HL6500, HL4500, HL4000, CLT50, Bosch Power Tools, Service engineers tools consisting of a good quality tool case containing pliers side cutters snipe nose pliers flat nose pliers water pump pliers hand operated de-soldering pump solder braid screwdrivers jewellers screwdrivers neon screwdriver soldering iron antistatic work mat with antistatic wrist band and coil cords and many more products to run your factory
GUIDE FOR SOLDERING STATIONS SOLDER AND SOLDERING IRONS Soldering made easy Types of irons Types of stations Why use a station and not just a mains iron What do I need for lead free soldering?
Why do I need to use lead free solder? This guide will help operators select and use correct soldering equipment to obtain effective results when soldering electronic components. Before looking at soldering you must also consider what other tools you need in order to perform the soldering to its best, if you are a service engineer you will need a tool case or better still a ready made or custom made tool kit Service engineers tools consist of a good quality tool case containing pliers side cutters snipe nose pliers flat nose pliers water pump pliers hand operated de-soldering pump solder braid set of screwdrivers jewellers screwdrivers neon screwdriver soldering iron a w61 or w101 will normally do for most applications and if the work is to be done on static sensitive products than a antistatic work mat with antistatic wrist band and coil cords is essential. If the work is to be done in a workshop then the tools are much the same but mains iron is normally replaced with a soldering station like the state of art self switching on off Weller WD1000T soldering station. Work benches are normally covered with antistatic or dissipative bench matting and termination points for coil cords and antistatic wrist bands are provided as well as antistatic or dissipative floor matting and in hi-tech works areas special clothing is provided and the use of instruments for checking static charges is in place. Selecting a suitable soldering iron is the most important decision which will affect your end results. We will start with the simplest soldering irons which are non temperature control main voltage as well as 12v dc and the heat is governed by the wattage of the soldering iron these irons are sold for as little as £4 and up to £30.00. Click here to see the Weller SP-SI Iron range. We recommend this range of SP-SI irons for DIY or a engineer who only needs to do very limited amount of soldering work whilst working on site. The next stage of soldering irons are main voltage irons and wattage ranges are from 25watt to 300watt and the best type of temperature control on these irons is a magnastat system which is basically a magnet on top of the tip set at pre determined temperature from 500f to 900f and once the tip reaches the pre determined temperature the magnet demagnetises switching the heat off until the tip temperature drops below the pre determined temperature and the iron is once again switched on. The Weller range of W61 W101 and the W201 irons are the market leaders for this type of irons and are amongst others they are used by travelling service engineers, leaded glass solder workers, battery pack makers, leaded roofing workers. Click here to see the Weller W61, W101 and W201 irons. Gas irons are also used for many applications and many service engineers prefer to carry these in their Tool kits, Many types of gas irons are available from £15.00 to over £200 in our opinion the best ones are WSTA1(wp60) WSTA2(pyropen junior) WSTA3 (pyropen) and the self ignition WSTA4 (piezo) irons which can be seen or purchased by Clicking here Soldering stations are mainly used in manufacturing or servicing workshops and normally consists of a power supply (with 115v or 230v input and 24v or 30v output for the soldering iron) a soldering iron and a bench stand. Starting Prices for soldering stations are from around £50 to several hundred £ and one must bear in mind the cost of replacement tips when ordering a new station as it would be false economy to save on the station and continually pay high prices for the replacement tips. Leading brands are Weller Pace Metcal. We will give a little insight on probably the most popular and best soldering station for several decades, the TCP IRON AND PS, PU power supplies The technology used for these stations is the same as the W61, W101 and the W201 irons, however the main voltage from the power supply to the soldering iron is dropped to 24v making it a safer environment for the operator, a comprehensive range of tips are produced by Weller to cover most sizes and shapes and are available in temperature ranges of 500f 600f 700f 800f and 900f. There is I newer version of this station available today which is the WTCP51 @ £79.46 and Click here to view or buy this station as well as tips and parts for the old TCP IRON Today’s technology has moved ahead and with new directive towards Lead Free Soldering the TCP iron and the PS51 Power supply are somewhat old hat and the new range of Weller stations are the WS81 (analogue) and the WSD81 (digital) These station give precise temperature, an ultra quick response time, light and easy to handle soldering iron, inexpensive replacement soldering tips, antistatic protection, which makes these stations a must for any workshop and specially if lead free solder is to be used in the future. Click here to buy or evaluate these superb Weller soldering stations What should I buy a soldering iron or a soldering station? Application and suggested soldering iron or stations: Home electrics, car electrics or service engineer Depending on how much you want to spend a basic 25w mains iron or w61 w101 or a gas iron maybe wsta4 Leaded glass workers ?? , w101 or w201 for heavy work Leaded roof work w201 or wsta4 Manufacturing or repair centres WSD81 WS81 or you may consider WTCP51 if working with standard 60/40 solder however looking long term the WS81 or WSD81 will be much better Lead free working WS81 and WSD81 STATIONS Solders The standard leaded solder is mainly used as 60/40 ready fluxed in sizes of 18 22 and 24awg and generally optimum working temperature is 700f (370c) The new directive is forcing most manufacturing companies to use unleaded solder which is available in many forms with or without silver and some lead free solders have very corrosive fluxes making them very tough on soldering iron tips. Lead free solder requires a more precise working temperature of around 350c in order to flow properly and therefore a suitable soldering station like WELLER WSD81 is highly recommended Click here to view or purchase 60/40 or lead free solder wire De-soldering methods A soldered joint which is improperly made will be unreliable and is likely to get worse in time. It may not have made any electrical connection at all, or could work initially and then cause the equipment to fail at a later date! It can be hard to judge the quality of a solder joint purely by appearances, because you cannot say how the joint actually formed on the inside, but by following the guidelines there is no reason why you should not obtain perfect results. A joint which is poorly formed is often called a "dry joint". Usually it results from dirt or grease preventing the solder from melting onto the parts properly, and is often noticeable because of the tendency of the solder not to "spread" but to form beads or globules instead, perhaps partially. Alternatively, if it seems to take an inordinately long time for the solder to spread, this is another sign of possible dirt and that the joint may potentially be a dry one. There will undoubtedly come a time when you need to remove the solder from a joint: possibly to replace a faulty component or fix a dry joint. The usual way is to use a de-soldering pump or a de-soldering station (More demanding users using CMOS devices might need a pump or station which is ESD safe.) Sometimes, it's effective to actually add more solder and then de-solder the whole lot with a pump or de-soldering station, if the solder is particularly awkward to remove. Care is needed, though, to ensure that the boards and parts are not damaged by excessive heat; the pumps themselves have a P.T.F.E. nozzle which is heat proof but may need replacing occasionally. De-Soldering stations are a must when de-soldering advance or multilayer boards. To buy or view the brand leaders weller de-soldering stations WMP1D WDD1A WSF80D WDD161 DSX80 WDD81D WDD101 OR WMD3 Click here For home user or service engineer an excellent alternative to a pump is to use de-soldering braid, also known as Solder-Wick. The TW No clean braid is a specially treated fine copper solder braid which draws molten solder up into the braid where it solidifies. To view or buy Solder braid or de-soldering hand pump Click here The best way to use solder braid is to use the tip of the hot iron to press a short length of braid down onto the joint to be de-soldered. The iron will subsequently melt the solder, which will be drawn up into the braid. Take extreme care to ensure that you don't allow the solder to cool with the braid adhering to the work, or you run the risk of damaging p.c.b. copper tracks when you attempt to pull the braid off the joint.
Here's a summary of how to make the perfect solder joint.
Troubleshooting Guide
Further Soldering information Soldering is a method of joining metal parts using a filler material (SOLDER) which has a melting temperature below 450 °C (842 °F). Soldering is distinguished from brazing by virtue of a lower melting-temperature filler metal; it is distinguished from welding by virtue of the base metal not melting during the joining process. In a soldering process, heat is applied to the parts to be joined, causing the solder to melt and be drawn into the joint by capillary action and to bond to the materials to be joined by wetting action. After the metal cools, the resulting joints are not as strong as the base metal, but have adequate strength, electrical conductivity, and water-tightness for many uses. Soldering is an ancient technique that has been used practically as long as humans have been making items out of metal.
The most frequent application of soldering is assembling electronic components to printed circuit boards (PCBs) using .WMP1D WDD1A WSF80D WDD161 DSX80 WDD81D WDD101 OR WMD3 stations (Click here) Another common application is making permanent but reversible connections between copper pipes in plumbing systems. Joints in sheet-metal objects such as food cans, roof flashing, drain gutters and automobile radiators have also historically been soldered, and occasionally still are. Jewellery and small mechanical parts are often assembled by soldering. Soldering is used to join lead came and copper foil in STAINED GLASS work. Soldering can also be used to effect a semi-permanent patch for a leak in a container or cooking vessel. Methods of soldering usingWELLER (IN OPINION BY FAR THE BEST WITH REGARDS TO QUALITY AS WELL AS PRICING SPECIALLY ON REPLACEMENT TIP AND AFTER SALE SERVICE) AND TW SOLDERING EQUIPMENT. SI25, SI75, FOR DIY AND OCCASIONAL USAGE,W60, W61, W100, W101, W200, W201, THESE IRONS ARE MAINS IRONS TEMPERATURE IS CONTROLLED BY THE USE OF MAGNASTAT AND THE ACTUAL TIP IS PRE SET TO TO 700 OR 800 DEG F TCP SOLDERING IRON, TCPS SOLDERING IRON, P51 POWER SUPPLY WTCP51 SOLDERING STATION, PTAA7,PTAA8, PTB7, PTCC7, PTCC8,PT07,PTO8, WSP80, WSP80FE, WDD1, WTCP STATION, WMP1D WDD1A WSF80D WDD161, WDD161V, DSX80, WDD81D, WDD101, OR WMD3 SYSTEMS (Click here for link) Other soldering station manufacturers and models are: PACE, METCAL, JBC, Soldering can be done in a number of ways, including passing parts over a small fountain in a bulk container of molten solder (Wave Soldering), heating assemblies by use of an Infrared lamp, or by using a point source such as an electronic soldering gun a brazing torch, or a hot-air soldering tool. Recently, reflow soldering is used almost exclusively for PCB assembly, sometimes followed by a wave-soldering or hand-soldering operation for oddly sized/shaped components. Though the base material is not melted in a soldering process, some of the base material's atoms do dissolve into the liquid solder. This dissolution process enhances the soldered joint's mechanical and electrical characteristics. A "cold solder joint" with poor properties may result if the base metal is not heated adequately to thoroughly melt the solder and cause this dissolution process to occur. Note that the distinction between soldering and brazing is arbitrary, with the only difference being the melting temperature of the filler material. A temperature of 450 °C is usually used as a practical cut off. Different equipment and/or fixturing is usually required since (for instance) most soldering irons cannot achieve high enough temperatures for brazing. Practically speaking there is a significant difference between the two processes -- brazing fillers have far more structural strength than solders, and are formulated for this as opposed to maximum electrical conductivity. Brazed connections are often as strong or nearly as strong as the parts they connect, even at elevated temperatures. "Hard soldering" or "silver soldering" (performed with high-temperature solder containing up to 40% silver) is also often a form of brazing, since it involves filler materials with melting points in the vicinity of, or in excess of, 450 °C. Although the term "silver soldering" is used much more often than "silver brazing", it may be technically incorrect depending on the exact melting point of the filler in use.
SoldersSoldering filler materials are available in many different alloys for differing applications. Traditionally, the eutectic alloy of 63% tin and 37% lead (or 60/40, which is almost identical in performance to the eutectic) has been the alloy of choice for most copper-joining applications. A eutectic formulation has several advantages for soldering; chief among these is the coincidence of the liquidus and solidus temperatures, i.e. the absence of a plastic phase. This allows for quicker wetting out as the solder heats up, and quicker setup as the solder cools. A non-eutectic formulation must remain still as the temperature drops through the liquidus and solidus temperatures. Any differential movement during the plastic phase may result in cracks, giving an unreliable joint. Additionally, a eutectic formulation has the lowest possible melting point, which minimizes stress on components during the soldering process. For environmental reasons, 'no-lead' solders are becoming more widely used. Unfortunately most 'no-lead' solders are not eutectic formulations, making it more difficult to create reliable joints with them. See complete discussion below; see also RoHS. Other common solders include low-temperature formulations (often containing bismuth), which are often used to join previously-soldered assemblies without un-soldering earlier connections, and high-temperature formulations (usually containing silver) which are used for high-temperature operation or for first assembly of items which must not become unsoldered during subsequent operations. Specialty alloys are available with properties such as higher strength, better electrical conductivity and higher corrosion resistance.
|
