EET 3124 Soldering 焊接Elements of Project Design, Analysis and Fabrication by Machine Methods手工焊接培训教材(7)PCB Soldering 电子线路板焊接wRead Chapter 17wSoldering alloying between solder and the metal parts between which an electrical connection is formed.手工焊接培训教材(7)Soldering Methods焊接方法wSeveral 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 热风回流焊接手工焊接培训教材(7)Solder Composition 焊料wSolder used in electronics is an alloy of tin and lead. 电子产品焊料是锡铅合金。wThe amount of tin ranges from 50 to 70%.锡所占比例为50% 到70%。wThe 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。手工焊接培训教材(7)Solder Melting Point Graph熔点固体状态液体状态熔融状态手工焊接培训教材(7)Solder Composition Cont.焊料wThe most common tin/lead ratio is 60/40.最常见锡铅比例为60/40。wEutectic 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。wDifferent ratios can be selected based on specific needs.根据需要可选择不同比例。手工焊接培训教材(7)Solder Alloying 焊接合金wWhen 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；wThis 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。手工焊接培训教材(7)Solder Forms 焊锡形状wSolder 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手工焊接培训教材(7)Solder Forms Cont.焊锡形状wFor 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 ）wMost solder wire is available with a core containing flux. 多数焊锡丝均有内孔手工焊接培训教材(7)Flux 助焊剂wFlux 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。wThe 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。手工焊接培训教材(7)Flux Cont. 助焊剂wFlux 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。wThis corrosive action can also damage components.助焊剂腐蚀性对元器件也有危害。手工焊接培训教材(7)Flux Cont.助焊剂wThere 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wChloride 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。手工焊接培训教材(7)Flux Cont.助焊剂wRosin 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。wRosin core fluxes are non-corrosive at room temperature.松香基助焊剂在室温下没有腐蚀性。wRosin core fluxes are corrosive at soldering temperatures.松香基助焊剂在焊接温度下具有腐蚀性。手工焊接培训教材(7)Flux Application 助焊剂使用wLiquid flux can be applied by:Wiping 擦拭Dipping 浸渍Spraying 喷雾Sponging 用海绵揩拭Foaming 发泡手工焊接培训教材(7)Flux Application Cont.助焊剂使用wPaste flux can be applied by:Wiping 擦拭Brushing 刷wRosin core solder uses flux that melts upon heat application during the soldering process.手工焊接培训教材(7)Flux Removal 清除助焊剂wAfter 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减少漏电机会手工焊接培训教材(7)Flux Removal Cont.清除助焊剂wSome 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 超声波清洗设备手工焊接培训教材(7)The Soldering Iron 烙铁wThe soldering iron consists of 4 basic parts:Tip 烙铁头Heating Element 加热单元Handle 手柄Power Cord 电源线手工焊接培训教材(7)The Soldering Iron Cont.烙铁wSoldering 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手工焊接培训教材(7)Tip Selection烙铁头选择wSoldering iron tips come in many styles.wTips 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。手工焊接培训教材(7)Tip Types烙铁头形状wChisel & 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。wBevel 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。手工焊接培训教材(7)Tip Types Cont.烙铁头形状wConical 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。wRadius Groove - Used on round components.半凹槽形用语圆形器件。手工焊接培训教材(7)Tip Types Cont. 烙铁头形状手工焊接培训教材(7)Soldering Iron Temperature烙铁温度wA 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。wSoldering 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。手工焊接培训教材(7)Soldering Iron Temperature Versus Wattage烙铁温度/功率手工焊接培训教材(7)Soldering Iron Tip Color Versus Temperature烙铁头颜色/温度手工焊接培训教材(7)Hand Soldering 手工焊接wBoards 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。手工焊接培训教材(7)Hand Soldering手工焊接手工焊接培训教材(7)Hand Soldering手工焊接wClean 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。手工焊接培训教材(7)Hand Soldering手工焊接wInsert 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。手工焊接培训教材(7)Hand Soldering 手工焊接wIts 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。手工焊接培训教材(7)Hand Soldering 手工焊接wApply 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。手工焊接培训教材(7)Hand Soldering 手工焊接wContinue 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。手工焊接培训教材(7)Hand Soldering 手工焊接wIt 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。 手工焊接培训教材(7)Solder Defects 焊接缺陷wSolder Peaking - Sharp point of solder protruding from a connection.Rapid removal of heat prior to solder becoming completely melted to liquid stage.w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。手工焊接培训教材(7)Solder Defects Cont.焊接缺陷wIncomplete wetting Alloying process not completed.w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。手工焊接培训教材(7)Solder Defects Cont.焊接缺陷wExcessive 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wCold 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。手工焊接培训教材(7)Solder Defects焊接缺陷wAn example of a dry joint - the solder failed to flow, and instead beaded to form globules around the wire. 手工焊接培训教材(7)Solder Defects Cont.焊接缺陷wTenfold excess of solder, and (extreme left) incomplete joint with poor coverage. There is no need to add more solder for luck. 手工焊接培训教材(7)Solder Defects Cont.焊接缺陷wOne example of several dry joints found within a commercial PSU adaptor for a computer peripheral. 手工焊接培训教材(7)Solder Defects Cont.焊接缺陷wA close-up reveals the terrible standard of soldering (and quality control), with a fracture visible on this ground/ earth joint. 手工焊接培训教材(7)De-soldering PCBs 去锡（解除焊接）wSeveral 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 真空去锡工作台手工焊接培训教材(7)De-soldering去锡wThe two solder joints to be de-soldered, to enable a faulty component to be removed. 手工焊接培训教材(7)De-soldering Cont.去锡wIf 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）手工焊接培训教材(7)De-soldering Cont.去锡wThe 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。手工焊接培训教材(7)De-soldering Cont.去锡手工焊接培训教材(7)De-soldering Cont.去锡wThe first joint, now de-soldered. The second joint will be de-soldered using braid.手工焊接培训教材(7)De-soldering Cont.去锡wSelect a suitable width of braid编织, and press it down onto the COLD joint using the hot tip of the iron. 手工焊接培训教材(7)De-soldering Cont.去锡wMolten 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! 毛细管吸附作用手工焊接培训教材(7)De-soldering Cont.去锡手工焊接培训教材(7)De-soldering Cont.去锡wThe component dropped out of the board after de-soldering. Sometimes, it may need persuading with pliers 钳子. 手工焊接培训教材(7)De-soldering Cont.去锡wClose-up shot of both joints, now de-soldered and ready for the replacement part to be fitted. 手工焊接培训教材(7)Dip Soldering 浸焊wPCB is physically dipped into a molten pot of solder.wBoard is cleaned and then fluxed prior to dipping.PCB预先上助焊剂。wUsually dipped by hand.手工焊接培训教材(7)Solder Pot Examples 锡炉手工焊接培训教材(7)Wave Soldering 波峰焊接wA conveyor system consisting of a fluxer, pre-heater and a solder wave.The fluxer is a aerated vat of flux (foam fluxer). The rising bubbles create a head of flux foam that is capable of penetrating plated through holes of the PCB.手工焊接培训教材(7)Wave Soldering波峰焊接手工焊接培训教材(7)Wave Soldering Cont.波峰焊接wThe preheater is used to reduce the risk of thermal shock to the PCB. Also aids in reducing the effect of device heat sinking and helps evaporate excess flux solvent.手工焊接培训教材(7)Wave Soldering Cont.wThe solder wave is formed by pumping molten eutectic solder vertically upward through a solder nozzle forming a standing wave.wMost solder waves have a bi-directional flow. 手工焊接培训教材(7)Wave Soldering Cont.波峰焊接wBridges and icicles will result if the wave soldering machine has too narrow a solder wave and the boards are run horizontal to the wave.手工焊接培训教材(7)Wave Soldering Cont.波峰焊接wInclining the conveyor and using a wave 3-4 inches in length will virtually eliminate the formation of these problems.倾斜角度、波峰宽度对连锡（桥接/短路）问题的影响。手工焊接培训教材(7)Wave Soldering Cont.波峰焊接手工焊接培训教材(7)