无铅选择焊工艺中OSP 板的通孔上锡

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无铅选择焊工艺中OSP 板的通孔上锡

Through hole wetting on an OSP finished PCB in a lead‐free selective soldering process无铅选择焊工艺中 OSP 板的通孔上锡Preface前言The ever increasing packaging density on PCB boards and the changeover to lead‐free alloys haveplayed a major role in the evolution and choice of PCB board finishes.The correct choice of a PCB finish usually involves the assessment of the pros and contras that areinherent to each finish and in most cases depends on the application and its requirements. Theserequirements can for example be: mechanical strength of the solder joint, planarity of the finish,pollution of the solder bath, storage time, degradation of the finish after reflow and last but not leastcost.

PCB 板上日益不断增加的封装密度及向无铅工艺的转型要求 PCB 的表面处理工艺有进一步的发展。选择正确的 PCB 表面处理工艺通常是根据产品的应用范围、对材料的要求和对各种不同表面处理工艺的自身特性进行评估决定的。这些通常来自于，例如：焊点的机械强度、板面的平直度、锡锅的洁净度、储存时间、回流后的表面降解以及成本。

# E; b- V& [# ~) u Despite its limitations in planarity, the HAL finish has succeeded to maintain a fairly wide acceptanceon most markets. Also NiAu has established itself as a reliable finish, although Au pollution in thesolder bath or solder joint might be of concern to some. Where I‐Sn appears to be more popular inEurope, I‐Ag seems to have the preference in the Americas. The OSP‐ finish is being used quite a lotin Asia but has less acceptance in the rest of the world.
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尽管有铅喷锡这种表面工艺在平直度上有一定的局限性，但是这种工艺很成功地广泛应用于大多数领域中。同样镍金板也是一种可靠性非常高的处理工艺，但是这种工艺在锡锅或焊点上的溶金也会带来一些问题。沉锡镀层在欧洲比较流行，而沉银镀层则在美国应用更加广泛。OSP板目前在亚洲有更多的市场。

Although, the OSP finish possesses some very interesting properties, it is seen by many as a low costsolution for low cost electronics. The main reason for this is that the solderability of the OSP coatingdegrades quite quickly after a lead‐free reflow process. This can result in problematic through holewetting in wave and selective soldering. Beside this disadvantage however, the coating has veryinteresting properties. The application process of OSP in PCB manufacturing is easy and has littleimpact on the solder mask, it has very high planarity, good storage stability and it is cheaper than allthe other finishes.

其中 OSP 板具有很吸引人的特性，它可以一定程度上降低生产成本。但是 OSP 涂层会在无铅回流之后快速降解而降低焊接性能，导致波峰焊和选择焊中通孔上锡成为一个让人头疼的问题。尽管有这一缺点，但是它生产简单，对绿油不会造成冲击，平直度非常高，易于储存并且廉价的特点使得它能够有很大的应用空间。

This case study focusses on finding the limitations of an OSP coating in terms of through hole wettingin a selective soldering process with two different lead‐free alloys. A standard SnCu based alloy andthe low melting point alloy LMPA™‐Q
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