锡膏百科名片solder paster也称焊锡膏，灰色或灰白色膏体，比重界乎:7.2-8.5。
一般为五百克密封瓶装，也有特别定做的如针铜包装或一公斤包装,与传统焊锡膏相比，多了金属成分。
于零到十度间低温保存(五至七度最佳),日前也有常温保存锡膏面市，效果仍不甚理想。
目录[隐藏]基本简介焊锡膏的主要成分及特性1.成分及其作用2.焊料粉无铅锡膏的成分及最佳合金成分比较1.根本的特性和现象2.最佳合金成分3.推荐锡膏-怎样设定锡膏回流温度曲线1.测试方法2.接受的方法3.普遍使用4.测试结果分析SMT中清除误印锡膏的正确方法焊锡膏和松香对电烙铁作用锡膏的保存与使用方法用途及分类及焊锡作用在焊锡中松香和焊锡膏各自的作用锡膏印刷锡膏印刷中的吞吐量与周期理解的锡膏回流过程锡膏异常解决方案改善锡膏印刷工艺[编辑本段]基本简介sold锡膏er paster也称焊锡膏,灰色或灰白色膏体,比重界乎:7.2-8.5.一般为五百克密封瓶装,也有特别定做的如针筒包装或一公斤包装,与传统焊锡膏相比,多了金属成分.于零到十度间低温保存(五至七度最佳),日前也有常温保存锡膏面市,效果仍不甚理想.通常使用3#粉径(25-45微米)之合金粉(因不同需要也有可能用到更细如4#及2.3#粗粉)与百分之八到十二的助焊膏在真空(氮气保护)环境之均速搅拌而成按环保分类为:有铅锡膏如:锡铅/锡铅银等与无铅锡膏如:锡银铜/锡铜/锡铋等按使用温度分为:高如锡铜或锡银铜系/常如锡银铋系/低温如锡铅铋/锡铋等锡膏按是否需清洗分为:清洗型和免洗型.按活性分为:高RA/中RMA/低R型广泛应用于SMT(表面元件贴装)行业![编辑本段]焊锡膏的主要成分及特性成分及其作用大致讲来, 焊锡膏的成分可分成两锡膏个大的部分, 即助焊剂和焊料粉(Flux&Solder powder)。
(一). 助焊剂的主要成分及其作用：A. 活化剂(Activation)：该成分主要起到去除PCB铜膜焊盘表层及零件焊接部位的氧化物质的作用, 同时具有降低锡,铅表面张力的功效；B.触变剂(Thixotropic)：该成份主要是调节焊锡膏的粘度以及印刷性能, 起到在印刷中防止出现拖尾、粘连等现象的作用；C. 树脂(Resins)：该成份主要起到加大锡膏粘附性，而且有保护和防止焊后PCB再度氧化的作用；该项成分对零件固定起到很重要的作用；D. 溶剂(Solvent)：该成份是焊剂成份的溶剂，在锡膏的搅拌过程中起调节均匀的作用，对焊锡膏的寿命有一定的影响；焊料粉(二)、焊料粉：焊料粉又称锡粉主要由锡铅合金组成，一般比例为63/3锡膏7; 另有特殊要求时，也有在锡铅合金中添加一定量的银、铋等金属的锡粉。
Solder Paste Printing ProcessPL-6 Technology Process SharingPrepared By: Rhoderic M. dela CuestaSMT ENGINEER5’S OF SOLDER PASTE PRINTING•Solder Paste - A homogeneous combination of solder particles (ranging in diameter from about 4 to 40 microns) Solder paste iscommonly applied by printing, dispensing, pre-forms, and manualmethods.•Stencil- A thin sheet of brass or stainless steel with openings that match the land pattern of the printed circuit board. Typically,solder paste are force applied through these openings onto the printed circuit boardcomponent pads.•Squeegee- A metal or rubber blade used in screen or stencil printing to wipe across the screen (stencil) to force solder paste throughopenings in the screen (stencil).•Support- A metal assistance of PWB that act as an underside brace to hold it in particular location.•Spatula- A tool commonly made of metal, plastic or ceramic used for mixing, spreading, cleaning and distributing solder paste prior printingprocess.THE SOLDER PASTE•Solder paste has been used in electronic assembly for more than 30 years now and it is a complex mixture of at least five elements: solder powder, flux vehicle ;(rosins/resins, activator, rheological control agents and solvent).1.0 Solder Powder- generally, they are widely available everywhere in theworld. Alloy composition depends on the need of manufacturing. Materialscience consideration are a key factor for the selection of alloy.•Alloys- A substance which are made of by melting two or moreelement/materials with different combination together. If twoelement are alloyed together, they are called binary alloy. If three,then is is called ternary alloy.Element Combination (%by weight)Tin (Sn)Lead (Pb)Silver (Ag)Copper (Cu)Alloy Name Type6040Sn60Pb40Binary6337Sn63Pb37Binary62362Sn62Pb36ag2Ternary3565Sn35Pb65Binary57385Sn57Pb38Ag5Ternary991Sn99Cu1Binary1.0 Solder Alloy composition- depends on customer requirements. Industry standard,it is important that the alloy composition passed requirements per J-STD-006. Most common alloy compositions are :Sn60Pb40, Sn63Pb37, Sn62Pb36Ag2, Sn96.5Ag3Cu0.5, Sn95.5Ag3.8Cu0.7 2.0 Should be spherical in nature.Among the solid shape,sphere has a lower has alower surface area per unitvolume. Thus, there arelower chances of surfaceoxidation compare to othersolid shape.1> Fines, 2>Satellites, 3>Elongated irregular particles, 4> Flattened particles, 5>loose conglomerates, 6>Welded conglomerates, 7> Angled surfaces, 8>Wrapped surfaces.3.0 PSD- Particle Size Distribution- powder size distribution range determine if the paste will pass through the stencil aperture opening. Too big cause a solder paste to clogged the stencil aperture, too small cause the solder paste to slump.Type Designation / J-Mesh Designation Particle Size Range Particle Size AverageSTD-005 for CrossReferenceType 2-200/+32575-4560Type 3-325/+50045-2535Type 4-400/+50038-2031Type 5-50025-1518Mesh Designation- the number defines how many opening in 1”X1” screen size had. If solder powder passes through a screen, it is describe as (-) minus else, (+) positive. 4.0 Oxide Content- refer to the a non-metallic compounds that might form on the powder, including carbonates and sulfides that could happen somewhere the process of alloy atomization to packaging.Atomization- A process of converting metal alloy into a very fine particles. Though there are a lot of way to atomized alloy, gas, centrifugal and ultrasonic atomization are very common since they have produce lower oxide on the solder powder.THE FLUX VEHICLESFlux formulations are the heart of solder paste manufacturer. Thus, detailedformulation information about this are hidden in public eyes.2.0 Rosin / Resin- At room temperature, rosin are solid, chemically inactive,an insulator, and soluble in solvents, but not in water. Rosin melts at about72°C (160°F) and the organic acids become active at around 108°C(225°F). Rosin are natural products while resin are synthetic and man-made. Resin are more preferred than rosin since the are much morecontrollable.3.0 Activators- also solid in room temperature. It is added to boost theperformance of the resin or rosin.4.0 Rheological additives- the most common additives are derivedfrom the castor oil. Castor oil are fatty acid composition used to furthercontrol the solder paste in term of printability and performance. Somesolder paste manufacturer are modifying castor oils but modificationare highly proprietary.5.0 Solvents-are added thus to make the solder paste more flexible tohandle and be mixed homogeneously .Solder paste are highly hygroscopic in nature. It tends to absorb moisture and water into the surrounding atmosphere. If moisture or water are absorb, the printing quality, solder powder materials and performance are greatly affected and deteriorated. This phenomena is detrimental to the process and product. Parallel to this, solder paste are also sensitive to heat and freezing temperature. Excessive heat causes separation of solder paste and flux. Freezing causes activator capability to descend thus reducing wetting ability.Transportation- should be as short as possible. Next day delivery should be practiced. Protect against excessive heat. Solder paste may be shipped in ice packs, dry ice, gel packs or other insulating material and should be discussed with SP Supplier.Storage- When received, check and stored ASAP. Solder paste should not remain on the receiving dock and should be stored in refrigeration at supplier recommendation. Refrigeration will double the shelf life of the material as compared to storing it at room temperature. Refrigeration also acts as an additional protector against unforeseen environmental changes. If solder paste is to be stored at room temperature, it is vital that the temperature and humidity be maintained at an appropriate level. Temperature should be per supplier recommendation.Solder Paste Inventory Control- To eliminate the cause for possible paste expiration, the use of the “first in, first out" (FIFO) inventory management is recommended — the oldest material in stock always should be used first.Thawing- Do not remove any seal, open or attempt to mix solder paste until it has warmed completely to room temperature. The typical warming or stabilization time for solder paste is four to eight hours. Do not force-warm solder paste, as this may cause flux separation or other rheological problems. A simple way to accomplish proper warming is to remove the solder paste from refrigeration the shift or the night before it will be used. If solder paste is used while it is cold, it will condense and draw moisture as it warms, possibly resulting in slump, spatter or other process defects. In addition, cold solder paste will have a dull appearance, be very difficult to stir, will not roll on the stencil or print correctly, and may stick to the squeegee blades.Solder Paste Mixing- It is necessary to ensure an even distribution (homogenous mixture) of any separated material throughout the paste. Manual or automatically stir the paste thoroughly in one direction depend on study (one to three minutes probably closer to one minute). If using spatula, never use to mixed with other type of SP.Printing Machine/Environmental Control -Variation to temperature and humidity is harmful to solder paste thus control is necessary. Control the temperature and humidity per solder paste suppliers recommendation or to plant internal study.Solder Paste Application Process -Controlling the level of solder paste on the stencil surface is vital to proper printing. It is better to add a smaller amount of paste more frequently than to add a large amount of paste less often. This method of control will ensure a constant turnover of paste, while keeping the freshest possible paste on the stencil.Squeegee刮 刀Spatula锡 浆 勺Every 60 minutes put the solder paste at the center.Long resting leads to poor printing due toharden solder paste每60分钟将锡浆往中间收集 一次,因为变硬的锡浆会影响 印刷 效果.Need to take out solder paste which unnecessary. Thesepaste gets harden and interfere to printing.除去不必要的锡浆 ,因为这地方的锡浆会变硬 而影响印刷效果在停产前和使用后 ,必须清洁 干净 .Must be cleaned after used, before long break or after completing production.Clean thoroughly after use使用过后彻底清洁丝 网StencilSTENCILThe stencil idea normally came from screen printing used in cloth illustration printing manufacturing. A screen mess had been applied with emulsionexposing only those area need to be printed. Drawback of using screen in solder paste is that control had been limited and use of metal squeegee is impossible.THE STENCIL“It takes a good stencil to get a good print, then automation helpsmake it repeatable”Anonymous •Stencil Materials- are selected based on cost and forming technology.•Materials used are brass, stainless steel, molybdenum, nickel, and plastic.•Stainless steel and brass are the most widely used materials inthe industry.•Molybdenum material had been promoted due to reportedimprovement in paste release from the stencil.•Nickel are a choice for electro-forming process but considerably costly.THE TECHNOLOGYChemical Etching ProcessCheapest method and a traditional manufacturing technology of stencil for majority of application. This is a subtracted process.1234Cleaning of metal clad 56Applying photo resist Imaging photo tool Developing Chemical EtchingRemoving photo resistChemical Etched Stencil is now ready for framing !!NOTE: Animation are for presentation purposes only. Deviation to the actual process might be noticed and seen.THE PROCESS1234Cleaning of metal clad 56Applying photo resist Imaging photo tool Developing Chemical EtchingRemoving photo resistProblem With Chemical Etch StencilChemical Etch stencil will exhibit a “hour glass profile”.Hour glass profile will hinders the smooth paste releaseto the stencil aperture hole.Other Common Problem With Chemical Etch Stencil Due to many process involve, variation was evident. Like most other, film shrink or expand relative to temperature and humidity. This cause accuracy problem and at the end printing problem. Tolerance can vary from 0.5 mils (12.7 microns) to as large as 2 mils (50.8 microns).Mis-registration of photo-film.Quality of chemically etched stencil = 1/Component Pitch.Laser Cut StencilA high cost form of stencil manufacturing. Like chemical etch, this is asubtracted process with higher accuracy of aperture hole to pad matching.Cutting is done in single side only thus repeatability was higher.The Process:Processing Gerber Data Cutting Image Inspection Framing DeliveryLaser Cut Stencil Common ProblemJagged aperture walls due to dross build-upElectropolishing -secondary microetching. This is done by placingchemically etch or laser cut stencil to atank filled with acidic solution andintroduce current to the solution foractivation. This process will remove thehigh points and rough points at the stencilsurface. Paste release will be good. Drawbacks:From this to thisTo shiny surface will reduce the coefficient offriction causing solder paste skipping. Skippinghappens when the solder paste is drag at thestencil top and rolling motion is not observed,Electroformed StencilA newest process of making an stencil and this is an additive process. This is a very high cost of stencil manufacturing though quality had been justified.Stencil thickness starts from zero and build to the desired thickness.1234Laminating a photosensitive dry film to a copper foil (0.25 mm thick)56Exposing to UV light for stencil pattern Developing where the apertureremain covered in copper mandrel.Put in the electroforming bath for nickel deposit.Removal of photo resist onthe aperture hole.Flexing.The ProcessElectroformed Stencil Common ProblemNickel were soft and it is more prone to damage but accuracy is higher.The stencil surface might betoo smooth that it will notallow the solder paste rollingmotion.Stencil Extra TreatmentElectro polishing - secondary micro etching. This is done by placing chemically etch or laser cut stencil to a tank filled with acidic solution and introduce current to the solution for activation.Nickel Plating - another additive process butnickel are deposit on a brass stencil material. Thisplating will only serve as a coating to smoothens thesurface and aperture wall for good paste release.Coating thickness range from 0.00030 to 0.00050inches (8 to 12 microns)Step-down/Step-up - A stencil treatment that willprovide a various paste deposition thickness. Usedfor product where a need of solder paste volumedeposit were fixed such as fine pitched on one sideand common component on the other side.THE STENCIL DESIGN GUIDELINESIPC-7525 provides general guidelines for solder paste stencil fabrication.In actual, aperture dimension follows different approaches from different person and uses.• Trial and Error - costly approach of determining the optimum range of aperture dimensions.• Inquiry to stencil manufacturer - they can only provide guidelines andrecommendations. Actual use and printing performance is not been given.• Experience - All rules are only guidelines. If it conforms and provide goodresult, it will be used as is otherwise new design with empirical dimensions aregiven.• Calculations - solder volume was calculated base on the actual solder filletrequired.Aperture Calculation Consideration - Response (Solder Volume)•Paste Release - The print-area ratio (PAR) is used as a guideline toquantify the paste-release capability of an aperture design, which also is shown in Figure 1. A PAR above 0.66 typically is acceptableIf stencil thickness was not given, formula above is used to compute such.•Solder Paste Metal Content - upon melting, the solder fillets will from solder joint. The volume will depends on the metal content of the solder paste used. Normally, metal content are in range of 85 to 91 percent.V =Xd sXds100 - XdfWhere:V = volume fraction of solder in solder paste.X = metal content (%w/w) of solder paste.ds = density of solder alloy.df = density of flux•Solder Paste Particle Size Distribution - solder paste alloy are atomized to form a powder. Sizes will depend on the the type of solder paste as shown in table below: (General Rule: minimum aperture width = 5 x (max. PSD)T y p eD e s ig n a tio n P e r J-S T D-005M e s hD e s ig n a tio nP e r A S T M-B214P a r tic le S iz eR a n g e inm ic r o n sP a r tic le S iz eA v e r a g e inm ic r o n sT y p e2-200/+32575–4560 T y p e3-325/+50045–2535 T y p e4-400/+50038–2031 T y p e5-50025- 1518• Aperture modification - If the aperture hole had been modified for some reason, component should stay in the PWB while in mounting process. Solder paste holding area might not be sufficient.•Tackiness of solder paste- A characteristic of solder paste that work to hold the components into into its place while in mounting process.Step-up / Step Down Design Consideration• Step-down Stencil - If there’s a need for a fine pitch printing but generally used thicker stencil to print other components. SHU2230 is one example of step downstencil.• Step-up Stencil - If there’s a need to print a thicker solder paste deposit to a small portion of the PWB. PWB utilizing module (WISMO, Wavecom modules) commonly used this kind of stencil. Generally, step-up stencil is much more expensive than that ofstep-down due to process involved. It needs thicker stencil area to scrape-out.K2K1ABITEM MIN MAXA0.130 mm (5 mils)B0.100 mm (4 mils)K1 2 mm (75 mils)K1 GRK20.65 mm (25 mils)(B x 36 )• NOTE: Data above are for design consideration and guideline only. Design varies per individual product study.A metal or rubber blade used in screen or stencil printing to wipe across the screen (stencil) to force solder paste through the aperture openings.Rubber Squeegee - The use of rubber squeegee into the production line causes wide variation on the quality performance. Rubber squeegeehardness depends on the aperture opening and should be measured using durometer. Too soft and it can cause “scooping effect”.Metal Squeegee - Common type of squeegee used in electronic industry due to its rigidity and strength. Metal squeegee are commonly made of stainless steel. Some are nickel plated to enhance solder paste printing rolling motion.Improved Metal Squeegee - In recent years, different innovation are implemented in squeegees. One here are squeegee tip metallurgical bonding process. Squeegees are infused with a special coatings on the tip causing a more smooth, low friction and more rigid squeegees.SQUEEGEES (SMART HEADS)Technology never stops. Researcher had made a quantum leap in advanced stencil printing technology. They had created rheometric pump print head.OTHERS:1.0 Closed-LoopTransducer PressureControl- Pressure issensed on the inside of thechamber walls for fluidpressure controlunattainable withconventional squeegeeblades. Software controlled,the chamber pressure isclosed-loop feedback intothe input cartridgesindependent of materialvolume.检查刮刀边沿是否平直,有无缺口和变形.Check the edge of the blade, should be straight, nocut and no deformation.金属刮刀 (METAL SQUEEGEE)有缺口的金属刮刀 (CUT METAL SQUEEGEE)缺口 (CUT)Side View側视图Use filler gauge here to measure any gap. Note thatthe squeegee should be perpendicular to granite stone.Filler gage should not be passing to any area in thesqueegee. 用塞尺测每一处缝隙，注意刮刀必须与平台垂直。
