手工焊接培训教材(7)

EET 3124 Soldering 焊接,Elements of Project Design, Analysis and Fabrication by Machine Methods,PCB Soldering 电子线路板焊接,Read Chapter 17Soldering alloying between solder and the metal parts between which an electrical connection is formed.,Soldering Methods焊接方法,Several Methods of SolderingHand 手工焊接Dip浸焊Wave波峰焊接Infrared Re-flow 红外线回流焊接Vapor Phase 热风回流焊接,Solder Composition 焊料,Solder used in electronics is an alloy of tin and lead. 电子产品焊料是锡铅合金。The amount of tin ranges from 50 to 70%.锡所占比例为50% 到70%。The ratio determines the strength, hardness and melting point of the solder.锡所占比例决定焊点的强度、硬度和熔点。,Solder Melting Point Graph熔点,固体状态,液体状态,熔融状态,Solder Composition Cont.焊料,The most common tin/lead ratio is 60/40.最常见锡铅比例为60/40。Eutectic solder has a tin/lead ratio of 63/37 and has almost no plastic transition state.共晶焊锡之锡铅比例为63/37，几乎没有熔融状态。Different ratios can be selected based on specific needs.根据需要可选择不同比例。,Solder Alloying 焊接合金,When solder melts onto a PCB connection, a thin film of metal is dissolved from the copper surface. 当焊锡在PCB焊盘上融化时，铜金属表面会有一层薄膜融解；This copper/solder mixture forms an alloy and establishes an electrically continuous joint.这个铜/焊锡形成合金并成为稳定的电气连接。,Solder Forms 焊锡形状,Solder is available in the following forms:Wire spools 锡丝（轴装）Bars锡条Sheets锡片Pellets锡球Washer and other specialized shapes锡制垫片及其它特殊形状,Solder Forms Cont.焊锡形状,For hand soldering, wire solder comes in ranges of 0.030” to 0.090” in diameter. 对于手工焊接，焊锡丝直径介于0.030” to 0.090” （ 0.762 mm to 2.286 mm ）Most solder wire is available with a core containing flux. 多数焊锡丝均有内孔,Flux 助焊剂,Flux is used to remove oxidation from the surface to be soldered.助焊剂用于除去焊接表面的氧化物。The flux removes the oxides from the metal surface and suspends them in solution where they float to the surface during the soldering process.助焊剂除去金属表面的氧化物，并在焊接过程中将之移至焊点表面。,Flux Cont. 助焊剂,Flux is corrosive and if left on the surface of the PCB, will deteriorate the conductor surfaces and reduce the resistance of the insulation between soldered connections.助焊剂具有腐蚀性，残留在PCB表面会使导体变质，并降低焊点间的绝缘性能。This corrosive action can also damage components.助焊剂腐蚀性对元器件也有危害。,Flux Cont.助焊剂,There are three major classifications of flux:Chloride (inorganic salts)氯化物 （无机盐）Organic (acids and bases)有机物Rosin松香/树脂Chloride and Organic fluxes are highly reactive at room temperature and are therefore not recommended for use in electronic construction.氯化物、有机物助焊剂在室温下活性很强，一般不用于电子产品制造。,Flux Cont.助焊剂,Rosin core fluxes are used almost exclusively for electronic construction.松香基助焊剂大多专用于电子产品制造。Rosin core fluxes are non-corrosive at room temperature.松香基助焊剂在室温下没有腐蚀性。Rosin core fluxes are corrosive at soldering temperatures.松香基助焊剂在焊接温度下具有腐蚀性。,Flux Application 助焊剂使用,Liquid flux can be applied by:Wiping 擦拭Dipping 浸渍Spraying 喷雾Sponging 用海绵揩拭Foaming 发泡,Flux Application Cont.助焊剂使用,Paste flux can be applied by:Wiping 擦拭Brushing 刷Rosin core solder uses flux that melts upon heat application during the soldering process.,Flux Removal 清除助焊剂,After the soldering process is complete, the flux must be removedImproves appearance 改善外观Eliminates possible corrosion problems避免可能的腐蚀问题Less chance of electrical leakage减少漏电机会,Flux Removal Cont.清除助焊剂,Some techniques for flux removal are:Use of flux remover sprays 助焊剂清洗剂Brushing with denatured alcohol用非饮用酒精刷洗Dipping PCB assembly into a solvent solution将PCBA浸入清洗液Ultrasonic equipment 超声波清洗设备,The Soldering Iron 烙铁,The soldering iron consists of 4 basic parts:Tip 烙铁头Heating Element 加热单元Handle 手柄Power Cord 电源线,The Soldering Iron Cont.烙铁,Soldering irons are selected based on:Size and style of tip尺寸和烙铁头形状Tip material烙铁头材料Required tip temperature 要求的烙铁头温度Tip temperature recovery time.烙铁头温度恢复时间,Tip Selection烙铁头选择,Soldering iron tips come in many styles.Tips are selected on the basis of personal preference and the goal of providing the largest contact area to the area to be soldered while minimizing the possibility of heat damage to surrounding leads and components.烙铁头选择依据焊盘大小、零件大小、焊接温度、元器件对温度的敏感性、个人喜好等。,Tip Types烙铁头形状,Chisel & Pyramid Used for hand wiring and general repair work. Allows large areas to be heated rapidly.凿子、棱椎形用于线材焊接和一般的修理工作。可以使较大区域迅速加热。Bevel Used for soldering terminal pad connections on single sided boards.斜角形用语焊接单面板上的接线端焊盘。,Tip Types Cont.烙铁头形状,Conical Used for high density wiring and heat sensitive parts.圆锥形用语焊接微小间距和温度敏感元器件。Radius Groove - Used on round components.半凹槽形用语圆形器件。,Tip Types Cont. 烙铁头形状,Soldering Iron Temperature烙铁温度,A tip temperature of 600 to 900 degrees F is sufficient for general purpose soldering.烙铁头温度600到900华氏度（316到482摄氏度）可以足够满足一般的焊接需要。Soldering irons are rated in watts. They are typically available from 15 to 60 Watts.烙铁功率一般为15到60瓦。,Soldering Iron Temperature Versus Wattage烙铁温度/功率,Soldering Iron Tip Color Versus Temperature烙铁头颜色/温度,Hand Soldering 手工焊接,Boards must be clean to begin with, especially if theyre not previously tinned with solder. Clean the copper tracks using e.g. an abrasive rubber block and clean with denatured alcohol.首先必须保证PCB洁净，特别是没有预镀锡的板。可以使用橡胶擦子或者非饮用酒精清洁PCB。,Hand Soldering手工焊接,Hand Soldering手工焊接,Clean the iron bit (tip) using a damp sponge. Iron featured is an Ungar Concept 2100 Soldering Station.,使用潮湿海绵清洁烙铁头。,Hand Soldering手工焊接,Insert components and bend the leads so that the part is held in place. 插入元件，将管脚折弯以固定元件。,Hand Soldering 手工焊接,Its usually best to snip the wires to length prior to soldering. This helps prevent transmitting mechanical shocks to the copper foil. 通常最好的做法是提前将零件脚剪至需要的长度。这可以预防对铜箔的机械冲击。,Hand Soldering 手工焊接,Apply a clean iron tip to the copper and the lead, in order to heat both items at the same time. 务必保持烙铁头洁净，并同时接触加热元件脚和焊盘。,Hand Soldering 手工焊接,Continue heating and apply a small amount of solder. Remove the iron and allow the solder joint to cool naturally.继续加热，并放入少量锡丝。移开烙铁以使焊点自然冷却。,Hand Soldering 手工焊接,It only takes a second or two, to make the perfect joint, which should be nice and shiny.只须12秒钟焊点就可以形成。良好的焊点应该整洁明亮。,Solder Defects 焊接缺陷,Solder Peaking - Sharp point of solder protruding from a connection.Rapid removal of heat prior to solder becoming completely melted to liquid stage.锡尖在焊锡未完全熔化成为液体状态之前快速移开烙铁所致。,Solder Defects Cont.焊接缺陷,Incomplete wetting Alloying process not completed.未润焊合金过程未完成Usually the result of insufficient heat and/or solder. 通常由加热不足或者焊锡不足导致。May also occur if contamination is on the terminal pad or soldering iron tip.也可能由于焊盘或者烙铁头污染所致。,Solder Defects Cont.焊接缺陷,Excessive solder lead contour not completely visible. 多锡（包焊）- 元件脚周线不可见。Reduce the amount of solder applied减少用锡量Cold solder joint dull-gray, grainy appearance.冷焊锡点呈暗灰色，表面粗糙。Result of insufficient heat.加热温度不足导致。,Solder Defects焊接缺陷,An example of a dry joint - the solder failed to flow, and instead beaded to form globules around the wire.,Solder Defects Cont.焊接缺陷,Tenfold excess of solder, and (extreme left) incomplete joint with poor coverage. There is no need to add more solder for luck.,Solder Defects Cont.焊接缺陷,One example of several dry joints found within a commercial PSU adaptor for a computer peripheral.,Solder Defects Cont.焊接缺陷,A close-up reveals the terrible standard of soldering (and quality control), with a fracture visible on this ground/ earth joint.,De-soldering PCBs 去锡（解除焊接）,Several aids to use for de-solderingSolder wick 吸锡芯绳Solder sucker吸锡器De-soldering bulb 去锡灯泡De-soldering tips 去锡尖头Extraction Tools 抽吸工具Vacuum de-soldering station 真空去锡工作台,De-soldering去锡,The two solder joints to be de-soldered, to enable a faulty component to be removed.,De-soldering Cont.去锡,If using a de-soldering pump, apply the iron first to melt the solder (1-2 seconds). 若使用吸锡器，先用烙铁使锡熔化。（12秒）,De-soldering Cont.去锡,The nozzle of the de-soldering pump is applied to the molten solder and the spring-loaded plunger is then released, drawing the solder up into the pump. Repeat if needed. 吸锡器吸嘴对准熔化的焊锡，释放弹簧活塞，吸走焊锡。可重复进行。,De-soldering Cont.去锡,De-soldering Cont.去锡,The first joint, now de-soldered. The second joint will be de-soldered using braid.,De-soldering Cont.去锡,Select a suitable width of braid编织, and press it down onto the COLD joint using the hot tip of the iron.,De-soldering Cont.去锡,Molten solder is drawn up by capillary action into the braid. Care not to overheat, or drag whiskers of solder over the board, nor let the braid solidify on the joint! 毛细管吸附作用,De-soldering Cont.去锡,De-soldering Cont.去锡,The component dropped out of the board after de-soldering. Sometimes, it may need persuading with pliers 钳子.,De-soldering Cont.去锡,Close-up shot of both joints, now de-soldered and ready for the replacement part to be fitted.,Dip Soldering 浸焊,PCB is physically dipped into a molten pot of solder.Board is cleaned and then fluxed prior to dipping.PCB预先上助焊剂。Usually dipped by hand.,Solder Pot Examples 锡炉,Wave Soldering 波峰焊接,A conveyor system consistin