深腔焊膏印刷

过去,在金属介质上进行倒装芯片组装时,如何在有凹槽空间的介质上实现焊膏印刷成为一大挑战.主要瓶颈是限流器有限区域内的模腔(深度小于2.0mm).一种做法是印刷焊膏时使用多孔焊膏喷嘴,其带来的问题在于喷嘴堵塞会造成焊膏量不一致.而喷嘴口的多重设计和焊膏尺寸的一致性对于提高焊膏性能至关重要.焊膏印刷技术已经使用多年.然而,传统的二维模版技术主要适用于平面介质.最近,相关模版制造商研发了一种新的模版技术,能够在小于100μm的凹槽上印刷.最新的研发成果是使用3D模版,配合一个专门设计的刮刀,以实现在受力变形的有限空间上良好的印刷效果.本文研究的是采用3D模版在凹槽深300μ m、小于2.0mm区域上实现焊膏印刷的技术,该技术可在有限空间内实现一致的焊膏印刷效果;此外,本文还研究了在间隔400μm、凹槽深150μm的区域上实现焊膏印刷的技术.3D模版可帮助焊膏印刷在凹槽空间内更好地控制焊膏质量.以下几个因素会影响焊膏印刷质量:焊料类型、模版布局、刮刀类型、凹槽形态及深度,此外还包含印刷参数.上述因素的相互作用使得在凹槽上进行连续的焊膏印刷成为可能.

Solder Stencil Printing on Deep Cavity

In the past when flip chip assembly on a metal substrate was implemented, these presented a challenge in solder paste printing using stencil on a cavity-formed space. The main restrictor is the cavity depth on a limited area (less than 2.0mm). Hence, an approach was to solder dispensing using a multi-hole dispense nozzle. This created challenges on the nozzle hole clogging resulting in inconsistencies and unacceptable volume deposited. Several iterations in the nozzle hole design and solder powder size consistency improved the performance but not to the expected level.Stencil printing technologies have been in use in the industry for many years. However, the conventional 2D stencil technology is primarily applicable and mostly used in fiat surfaces. Recently, stencil manufacturers developed new stencil technology capable of printing on a 100 microns depth or less. The most recent development of printing solder paste is by using a 3D stencil paired with a specially designed squeegee to achieve a good and consistent print deposit in constrained and limited spaces. This study is on solder paste printing using 3D stencil on a 300-micrometer cavity and less than 2.0-millimeter area. It is feasible to form an array of solder deposits on the limited-spaced cavity. Another study is printing on a 150-micrometer cavity spaced at 400 micrometers apart. The 3D stencil allows for a more controlled solder deposit on cavity-formed spaces.Several factors affect the quality of print deposits - solder type, stencil layout, type of squeegee, cavity layout and depth, as well the printing parameters used. The interactions of these elements make possible solder paste printing on a deep cavity spaced in array.