SMT全技術-第二集.doc

表面贴装技术
SMT的特點
為什麼要用表面貼裝技術(SMT)？
為什麼在表面貼裝技術中應用免清洗流程？
回流焊缺陷分析（錫珠、錫橋、開路）
SMT有關的技術組成
滴膠機(活塞式、阿基米德式、無接觸式）
貼片機（拱架型、轉塔型）
SMT的特點
1. 組裝密度高、電子產品體積小、重量輕，貼片元件的體積和重量只有傳統插裝元件的1/10左右，一般採用SMT之後，電子產品體積縮小40%~60%，重量減輕60%~80%。
2. 可靠性高、抗振能力強。焊點缺陷率低。
3. 高頻特性好。減少了電磁和射頻干擾。
4. 易於實現自動化，提高生產效率。
5. 降低成本達30%~50%。節省材料、能源、設備、人力、時間等，
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為什麼要用表面貼裝技術(SMT)？
1. 電子產品追求小型化，以前使用的穿孔插件元件已無法縮小
2. 電子產品功能更完整，所採用的積體電路(IC)已無穿孔元件，特別是大規模、高集成IC，不得不採用表面貼片元件，
3. 產品批量化，生產自動化，廠方要以低成本高產量，出產優質產品以迎合顧客需求及加強市場競爭力
4. 電子元件的發展，積體電路(IC)的開發，半導體材料的多元應用
5. 電子科技革命勢在必行，追逐國際潮流
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為什麼在表面貼裝技術中應用免清洗流程？
· 生產過程中產品清洗後排出的廢水，帶來水質、大地以至動植物的污染。
· 除了水清洗外，應用含有氯氟氫的有機溶劑(CFC&HCFC)作清洗，亦對空氣、大氣層進行污染、破壞。
· 清洗劑殘留在機板上帶來腐蝕現象，嚴重影響產品質素。
· 減低清洗工序操作及機器保養成本。
· 免清洗可減少組板(PCBA)在移動與清洗過程中造成的傷害。
· 仍有部分元件不堪清洗。
· 助焊劑殘留量已受控制，能配合產品外觀要求使用，避免目視檢查清潔狀態的問題。
· 殘留的助焊劑已不斷改良其電氣性能，以避免成品產生漏電，導致任何傷害。
· 免洗流程已通過國際上多項安全測試，證明助焊劑中的化學物質是穩定的、無腐蝕性的。
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回流焊缺陷分析：
· 錫珠(Solder Balls)：原因：1、絲印孔與焊盤不對位，印刷不精確，使錫膏弄髒PCB。 2、錫膏在氧化環境中暴露過多、吸空氣中水份太多。3、加熱不精確，太慢並不均勻。4、加熱速率太快並預熱區間太長。5、錫膏幹得太快。6、助焊劑活性不夠。7、太多顆粒小的錫粉。8、回流過程中助焊劑揮發性不適當。錫球的工藝認可標準是：當焊盤或印製導線的之間距離為0.13mm時，錫珠直徑不能超過0.13mm，或者在600mm平方範圍內不能出現超過五個錫珠。
· 錫橋(Bridging)：一般來說，造成錫橋的因素就是由於錫膏太稀，包括 錫膏內金屬或固體含量低、搖溶性低、錫膏容易榨開，錫膏顆粒太大助焊劑表面張力太小。焊盤上太多錫膏，回流溫度峰值太高等。
· 開路(Open)：原因：1、錫膏量不夠。2、元件引腳的共面性不夠。3、錫濕不夠(不夠熔化、流動性不好)，錫膏太稀引起錫流失。4、引腳吸錫(象燈芯草一樣)或附近有連線孔。引腳的共面性對密間距和超密間距引腳元件特別重要，一個解決方法是在焊盤上預先上錫。引腳吸錫可以通過放慢加熱速度和底面加熱多、上面加熱少來防止。也可以用一種浸濕速度較慢、活性溫度高的助焊劑或者用一種Sn/Pb不同比例的阻滯熔化的錫膏來減少引腳吸錫。
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SMT有關的技術組成
· 電子元件、積體電路的設計製造技術
· 電子產品的電路設計技術
· 電路板的製造技術
· 自動貼裝設備的設計製造技術
· 電路裝配製造工藝技術
· 裝配製造中使用的輔助材料的開發生產技術
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滴膠機
· 活塞式滴膠泵：
1. 工作原理：壓縮空氣送入膠瓶(注射器)，將膠壓進與活塞室相連的進給管中，當活塞處於上衝程時，活塞室中填滿膠，當活塞向下推進滴膠針頭時，膠從針嘴壓出。滴出的膠量由活塞下沖的距離決定，可以手工調節，也可以在軟體中控制。
2. 特點：高速度、對膠劑粘度的低靈敏度。

· 阿基米德式滴膠泵：
1. 工作原理：壓縮空氣送入膠瓶(注射器)，將膠壓進進給管中，膠流經以固定時間、特定速度旋轉的螺杆。螺杆的旋轉在膠劑上形成剪切力，使膠劑沿螺紋流下，螺杆的旋轉在膠劑上不斷加壓，使其從滴膠針嘴流出。
2. 特點：具有膠點點徑無固定限制的靈活性。可通過軟體進行調整。但是滴大膠點時，螺杆旋轉時間長，會降低整台機器的產量。另外，膠劑的粘度和流動特性會影響其穩定性。

· 無接觸式滴膠泵：
1. 工作原理：壓縮空氣送入膠瓶(注射器)，將膠壓進與活塞室相連的進給管中，在此加熱，溫度受控制，以達到最佳的始終如一的粘性。使用一個球座結構，膠劑填充由於球從座中縮回留下的空缺。當球回來時，由於加速產生的力量斷開膠劑流，使其從滴膠針嘴噴射出，滴到板上形成膠點。
2. 特點：1)、消除了傳統方法產生的膠點拉尾。2)、沒有滴膠針的磨損和與其他零件干涉的問題。3)、無針嘴損壞。4)、無由於基板彎曲和被針嘴損害的報廢
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貼片機：
· 拱架型(Gantry)：
1. 元件送料器、基板(PCB)是固定的，貼片頭(安裝多個真空吸料嘴)在送料器與基板之間來回移動，將元件從送料器取出，經過對元件位置與方向的調整，然後貼放於基板上。由於貼片頭是安裝於拱架型的X/Y座標移動橫樑上，所以得名。
2. 對元件位置與方向的調整方法：1)、機械對中調整位置、吸嘴旋轉調整方向，這種方法能達到的精度有限，較晚的機型已再不採用。2)、鐳射識別、X/Y坐標系統調整位置、吸嘴旋轉調整方向，這種方法可實現飛行過程中的識別，但不能用於球柵列陳元件BGA。3)、相機識別、X/Y坐標系統調整位置、吸嘴旋轉調整方向，一般相機固定，貼片頭飛行劃過相機上空，進行成像識別，比鐳射識別耽誤一點時間，但可識別任何元件，也有實現飛行過程中的識別的相機識別系統，機械結構方面有其他犧牲。
3. 這種形式由於貼片頭來回移動的距離長，所以速度受到限制。現在一般採用多個真空吸料嘴同時取料(多達上十個)和採用雙梁系統來提高速度，即一個梁上的貼片頭在取料的同時，另一個梁上的貼片頭貼放元件，速度幾乎比單梁系統快一倍。但是實際應用中，同時取料的條件較難達到，而且不同類型的元件需要換用不同的真空吸料嘴，換吸料嘴有時間上的延誤。
4. 這類機型的優勢在於：系統結構簡單，可實現高精度，適於各種大小、形狀的元件，甚至異型元件，送料器有帶狀、管狀、託盤形式。適於中小批量生產，也可多台機組合用於大批量生產。
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· 轉塔型(Turret)：
1. 元件送料器放于一個單座標移動的料車上，基板(PCB)放於一個X/Y坐標系統移動的工作臺上，貼片頭安裝在一個轉塔上，工作時，料車將元件送料器移動到取料位置，貼片頭上的真空吸料嘴在取料位置取元件，經轉塔轉動到貼片位置(與取料位置成180度)，在轉動過程中經過對元件位置與方向的調整，將元件貼放於基板上。
2. 對元件位置與方向的調整方法：1)、機械對中調整位置、吸嘴旋轉調整方向，這種方法能達到的精度有限，較晚的機型已再不採用。2)、相機識別、X/Y坐標系統調整位置、吸嘴自旋轉調整方向，相機固定，貼片頭飛行劃過相機上空，進行成像識別。
3. 一般，轉塔上安裝有十幾到二十幾個貼片頭，每個貼片頭上安裝2~4個真空吸嘴(較早機型)至5~6個真空吸嘴(現在機型)。由於轉塔的特點，將動作細微化，選換吸嘴、送料器移動到位、取元件、元件識別、角度調整、工作臺移動(包含位置調整)、貼放元件等動作都可以在同一時間週期內完成，所以實現真正意義上的高速度。目前最快的時間週期達到0.08~0.10秒鐘一片元件。
4. 此機型在速度上是優越的，適於大批量生產，但其只能用帶狀包裝的元件，如果是密腳、大型的積體電路(IC)，只有託盤包裝，則無法完成，因此還有賴於其他機型來共同合作。這種設備結構複雜，造價昂貴，最新機型約在US$50萬，是拱架型的三倍以上。
A
· "A" Wave. Wave, "A"
· Å. Angstrom
· A/D Converter. Analog-To-Digital Converter
· Absorption. The retention of moisture by a substance.
· Accelerated Stress Test. A test to deliberately produce a failure.
· Acceptable Quality Level (AQL). Maximum number of defects per 100 pieces that are allowable.
· Acceptance Tests. Tests deemed necessary to determine the acceptability of products.
· Accuracy. (1) The ability to hit the target. (2) Conformity of a measured value to the actual value of the sample.
· Acoustic Microscopy. A nondestructive test that produces high resolution ultrasonic images, often used for inspecting component lid seals and die attach within components.
· Acrylic. A monomeric acrylate or methacrylate (acrylic acid or a derivative thereof) cured in a polymerization reaction brought on by ultraviolet energy, heat, or a combination of the two.
· Acrylic Resin. A thermosetting, transparent, flame resistant resin.
· ACS. American Chemical Society
· Activated Carbon. A water treatment medium, commonly used for de-chlorination and for reducing organic chemicals and radon from water. Activated Carbon is produced by heating carbonaceous substances (bituminous coal or cellulose-based substances such as wood or coconut shell) to 700°C or less in the absence of air to form a carbonized char, and then activating (oxidizing) at 800 to 1000°C with oxidizing gases such as steam and carbon dioxide to form pores, increasing the surface area of this adsorbent material. It can be in block, granulated, or powdered form.
· Activated Rosin Flux. Flux, Rosin Activated
· Activator. Thermally reactive compounds (such as amine hydrochlorides or various halides) that break down at elevated temperatures and enhance the ability of a flux to remove oxides and other contaminants from surfaces being joined.
· Active Components. Electronic components such as semiconductors, transistors, diodes, etc., that can change the characteristics applied electrical signal.
· Active Hold-Down. The process of pressing a component lead directly in contact with a bonding pad during soldering to ensure intimate contact between the lead and pad.
· Activity. (1) Activities may consist of moving or handling materials and components, changing machine or tool settings, turning equipment on or off, etc. Poorly control of activities can create process variability and varying quality. (2) Flux Activity
· ADC. Analog-To-Digital Converter
· Additive Plating. Plating, Additive
· Adhesion. The state in which two surfaces are held together by interfacial forces which may consist of valence forces or interlocking action.
· Adhesion, Mechanical. Adhesion between surfaces in which the adhesive holds the parts together by interlocking action.
· Adhesive. A substance capable of holding material together by surface attachment.
· Adhesive, Anisotropic. An adhesive with a low concentration of metal particles to permit conduction in the z-axis only.
· Adhesive, Conductive. A two part system comprised of a polymer base and a conductive filler.
· Adhesive Failure. Failure resulting from insufficient bond between the adhesive and one or both substrates. Adhesive strips away from substrates.
· Adhesive Specific. Adhesion between surfaces which are held together by valence forces or molecular bonding.
· Adhesive Tensile Loading. When the acting forces are applied at right angles to the plane of the adhesive. The tensile strength of a bond is the maximum tensile load per unit area, required to break the bond expressed in pounds per square inch.
· Adhesive, Thermoplastic melt on application. The process is reversible.
· Adhesive, Thermoset undergo a chemical change during heating. The change is not reversible. Epoxies and acrylics are thermosets.
· AFM. See atomic force microscope.
· Ag. Chemical symbol for the element silver.
· Aging. The change in the properties of a material over time and under varying conditions of humidity, temperature, pressure, etc.
· Air Knife. (1) A mechanical air pressure amplifier. (2) A plenum with a narrow opening used develop high velocity air from a low pressure air source to (a) dry / remove liquid films from surfaces (b) control the coating of surfaces, or (c) heat or cool.
· Algorithm. A set of rules specifying a sequence of actions taken to solve a problem.
· Alignment Hole. Tooling Hole
· Alloy. A substance made by melting two or materials together.
· Alumina. A common substrate material composed of approximately 95% Al2O3.
· Ambient Level. The values of signals and noise that exist at a test location when the device under test is not active.
· Amorphous Phase. Non-crystalline Most plastics are amorphous at processing temperature. Many retain this strength under normal temperatures.
· Analog Circuit. An electrical circuit that provides a continuous relationship between its input and output.
· Analog-To-Digital Converter (ADC or A/D converter). An electronic circuit that produces a digital output directly proportional to an analog signal input.
· Anechoic Chamber. An enclosure especially designed with walls that absorb sound or radiation, creating an essentially free-field environment for testing.
· Angle Of Attack. The angle between the squeegee and the stencil or screen.
· Angstrom. A unit of length equal to one hundred-millionth (10^-8) of a centimeter, often used to specify radiation wavelengths.
· Anion. An ion with a negative charge. An anion [such as chloride (Cl-), nitrate (NO3-), bicarbonate (HCO3-), or sulfate (SO4--)] may result from the dissociation of a salt, acid, or alkali.
· Anion Exchange. Ion Exchange. A water conditioning process.
· Antioxidants. Compounds that retard the rate of oxidation of a polymer.
· Anisotropic. Exhibiting different physical properties in different directions.
· Anisotropic Adhesive. Adhesive Anisotropic
· Annular Ring. The pad area that remains after a hole is drilled through the pad.
· ANSI. American National Standards Institute
· Antistatic Materials resist turbocharging more than ?00 volts.
· Anti-Pad. The area of copper etched away around a via or a plated through-hole on a power or ground plane, thereby preventing an electrical connection being made to that plane.
· AOI. Automated Optical Inspection
· Application-Specific Integrated Circuit (ASIC). An IC device whose function is designed for a specific application(s).
· Aperture. An opening in a stencil or screen.
· Aperture, Chemical Etched. An opening in metal stencil created by coating the metal foil with photoresist, exposing an image both sides the resist using a phototool, and etching the foil from both sides.
· Aperture, Electroformed. An opening in stencil formed by imaging a photoresist on a substrate and then plating the nickel foil around the resist to the desired thickness.
· Aperture, Electropolished. An electrolytic post-process that "smooths" the walls of aperture walls to improve solder paste printing.
· Aperture Files. Precise x-y location and shape of all apertures required on a printed circuit board.
· Aperture, Laser Cut. An opening in a metal stencil created by using Gerberâ and aperture data to position a laser cutting head.
· Aperture, Trapezoidal. An aperture with the board side opening 1 to 2 mils larger than the squeegee side opening.
· API. Application Program Interface
· Application Program Interface. The interface between the application's software and the application platform.
· Application Software. A program that performs a specific service or solves a particular problem.
· AQL. Acceptable Quality Level
· Aqueous. A water soluble.
· Aqueous Cleaning. Cleaning, Aqueous
· Architecture. A structured set of protocols that implement the functions of the system.
· Array. A group of components arranged on rows and columns.
· Artwork. A phototool used to create (1) features during printed circuit board fabrication or (2) apertures on a screen or a chem-etched stencil.
· Artwork Generation. The process of transferring the CAD circuit layout to reproducible artwork for use by stencil and printed circuit board fabricators.
· Artwork Master. Artwork used to produce production masters.
· ASIC. Application Specific Integrated Circuit
· ASME. American Society of Mechanical Engineers
· Aspect Ratio. (1) Thickness of a printed circuit board to the diameter of the smallest hole. (2) Thickness of a stencil to the width of the smallest aperture.
· Assembler. A program that translates mnemonics into binary codes that run on a computer.
· Assembly. A functional subdivision of a component, consisting of parts or subassemblies that perform functions necessary for the operation of the component as a whole. Examples: regulator assembly, power amplifier assembly, gyro assembly, etc.
· AST. Accelerated Stress Testing
· ASTM. American Society for Testing and Materials
· Asynchronous. An action that takes place at an arbitrary time, without synchronization to a reference timer or clock.
· ATE. Automatic (Automated) Test Equipment
· Atm. Atmosphere pressure
· Atomic Force Microscope (AFM). A microscope that works by bringing a fine needle right up to the surface of a semiconductor and tracing the topography of the material. AFMs are an alternative to scanning electron microscopes as a means of measuring and monitoring the widths and heights of critical dimensions on an integrated circuit die.
· Au. Chemical symbol for the element gold.
· Automated Optical Inspection (AOI). A mechanized visual inspection process.
· AWG. American Wire Gage
· Axial Lead. Lead wire extending from a component or module body along its long axis.
· Axial Leaded Components are usually cylindrical in shape and have leads exiting from opposite ends along its long axis.
· Azeotrope. A liquid mixture with a constant maximum or minimum boiling point lower or higher than the boiling points of its components and with the capacity to distill without change in composition.
A | B | C | D | E | F | G | H I | J | K | L | M | N | O
P | Q | R | S | T | U | V | W | X | Y | Z | NON-LETTER
B
· B-Stage Resin. An intermediate stage in curing a thermoset resin. Prepreg
· Back End Of The Line (BEOL). Test, assembly, and packaging of wafer manufacturing.
· Ball Bonding. Bonding, Ball
· Ball Grid Array (BGA) is surface mount technology IC package that provides electrical advantage of shorter signal and power paths and the mechanical advantage of greater interconnects and higher lead pitch, while decreasing package size.
· Bare Board. An unpopulated printed circuit board.
· Bare Die. An unpackaged integrated circuit.
· Barrel. The cylinder formed in the drilled through hole in a printed circuit board.
· Base Board. Base Material
· Base Material. In printed circuit board fabrication, the insulating laminate where the conductor pattern is formed.
· Batch. An entity that represents the production at any point in the process. A batch is a running control recipe. The material that is being produced or that has been produced by a single execution of a recipe is also considered a batch.
· Batch Control. Consists of a sequence of one or more steps (phases) that must be performed in a defined order for a finite period of time to process finite quantities of input material to produce finished product.
· Batch Manufacturing. Manufacturing in groups, lots or batches in which each part or finished good is identical.
· Batch Processing. The method adopted when the require