Step5胶粘剂与点胶.docVIP

胶粘剂与点胶 Adhesives, Epoxies and Dispensing By Jeff Bowin, Brian J. Toleno, Ph.D. and Neil Poole, Ph.D. 随着制造商们不断强化电路板组件功能的过程，电路板单位面积的元件数也随之增加。在波峰焊接之前，双面组装必须采用表面贴片胶（SMA）将元件附着在组件的底面上。制造商们可以采用两种方式以实现组件上更高的表面贴片胶（SMA）涂敷量，即高速点胶和丝网印刷。 As manufacturers design more functionality into circuit board assemblies, the number of components per unit area increases. On mixed technology double-sided assemblies, surface mount adhesives (SMA) are used to adhere components to the bottom side of the assembly prior to wave soldering. To place a high volume of SMA deposits onto an assembly, manufacturers have two options: high-speed dispensing or screen printing. 液态表面贴片胶（SMA）除必须保证在高速状态下具有优异的点胶性能和模板印刷性能以外，还必须具有足够的润湿性能和湿强度，以保证在胶粘剂固化过程中元件保持正确的位置。胶粘剂固化后须具有足够的强度以保证波峰焊接过程中元件不至于脱离电路板，同时，保证焊接后胶粘剂不致影响电路的正常工作。 In addition to the ability to be dispensed or stencil printed at high speeds, the liquid SMA must have sufficient wet or green strength to hold a component in position from placement through cure. The cured adhesive must be strong enough to secure the surface mount component to the board during wavesolder operation. After soldering, the adhesive must not affect circuit operation. 胶粘剂必须保证在高速点胶过程中形成胶点，并且胶点具有一致的外形和尺寸，胶点必须具有一定的高度。胶粘剂还必须具备高湿强度、固化迅速以及固化周期内不塌落等特点，同时，在波峰焊接过程中，在保证具有高强度的同时，胶粘剂还应该具有一定的弹性，并应具有良好的热扩散阻值，同时，优异的电学性能是优质胶粘剂的关键性能。 The adhesive must enable high-speed application of small dots, while delivering consistent dot profile and size. Dot profiles must be high, and the adhesive must be non-stringing. The adhesive should provide high green or wet strength, cure rapidly, be non-slumping during the cure cycle, and provide high strength combined with flexibility and resistance to thermal exposure during the wavesolder process. Finally, good electrical properties are critical. 针筒式点胶 Syringe Dispensing 现阶段，点胶机可实现每小时5万胶点甚至更高的点胶速率，而新一代表面贴片胶则相应地为高速点胶过程提供了所需的材料流变性能。了解材料流变性能的适当组合是设计一台可重复性点胶系统最为重要的步骤。 The speed of current-generation dispense machines is approaching, and even exceeding, 50,000 dots p