标准SMT工艺流程图.ppt

Titel, Subtitel Standard SMT Process Flowchart/标准SMT工艺流程图 What constitutes a good soldering?良好焊锡由什么组成? Solder is an alloy used as a medium to bond the components and PCB substrate mechanically, thermally and electrically. 焊锡是一种合金,它是用来作为通过机械,热力,电力的方法焊接元件和 PCB的媒质. A joint reliability is dependent on the remain flux residue, soldering time, thermal mismatch, etc. 焊点的可靠性决定于助焊剂残余物,焊接时间,受热不均,等等. Paste Description/锡浆描述 Alloy Type - Depends on operating temperature e.g Sn63 Pb37 合金类型-根据操作温度,例如:Sn63 Pb37 Mesh Size - Dependent on the application pitch size e.g -325/+500 for 20 mils QFP 网孔尺寸-根据应用粒径尺寸,例如: -325/+500用于20mils QFP. Flux - Depends on criteria such as probe testable, e.g NC-SMQ 92J 助焊剂-根据标准,例如探测器可实验性,例如NC-SMQ 92J. Metal Load - Depends on flux type and application method. 金属添加-根据助焊剂类型和应用方法. Packaging - Jar / Syringes / Cartridges 包装方法-广口瓶/注射器/药筒 Functions of Flux in Soldering/在焊接中助焊剂的功能 Remove surface oxides on the substrate as well as powder Act as oxidation barrier during reflow 清除基底表面氧化物，同时焊锡粉末在回流过程中阻碍氧化。 Lower the surface tension of the paste to form a more efficient wetting joint 降低锡浆表面张力以便形成更有效的焊点。 Flux Vehicle Chemistry/助焊剂载体化学性质 Resin - modified / synthetic rosin 松香-人工改良的/人工合成的松香 - act as oxidation barrier/阻碍氧化 tacky and viscous/带有粘性 Solvent - dissolved chemicals/constituents 溶剂-溶解的化学物质/成分 - evaporate during preheat/在预热过程中蒸发 - control viscosity and rheology/控制粘度及流动性 Flux Vehicle Chemistry (Cont’d)/助焊剂载体化学性质(Cont’d) Activator - cleaning agent during reflow 催化剂-在回流过程中的清洁剂 - Dissolves oxides off the metal surfaces promote wetting 溶解脱离金属表面的氧化物提高焊接效果 Additives - regulate viscosity and paste stability 添加剂-控制粘度及锡浆稳定性 Solder Powder Size – Mesh/焊锡粉末尺寸—网孔 Mesh Number gives the number of wires per inch of screen. 网孔的数目确定了钢网每英寸金属线的数目。 For instance, a 200 mesh screen has 200 wires per inch. Each wire is 52 microns in diameter, and the width of each opening is 75 microns. Consequently, a 200 mesh screen allows 75 micron