Implementation of Lead-Free Wave Soldering Process
Implementation of Lead-Free Wave Soldering Process
复制标题
无铅波峰焊工艺的实施
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
M. Alatalo
中科院分区：
文献类型：
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作者：
Elina Havia;E. Bernhardt;Timo Mikkonen;Henri Montonen;M. Alatalo
用不同的波峰焊接参数进行了一系列测试，以检验无铅波峰焊接过程中所获得的焊接质量。焊料为锡-银-铜(SAC)合金。焊料罐温度设置在250°C到275°C之间。最常用的罐温度为260℃，这是SAC焊料通常使用的罐温度。其他考察的工艺参数包括焊料接触时间、焊接气氛、预热温度、助焊剂类型和助焊剂数量。测试系列包括不同的无铅印刷电路板表面处理。由于SAC合金的表面张力较高，经常会观察到焊桥和未焊接的SMD元件。通过优化焊接工艺，可以将这些缺陷的数量降至最低。无铅波峰焊接的主要问题之一是难以焊接热质量较大的通孔元件。通常，只有在较长的焊料接触时间和较高的焊料温度下，才能焊接热质量较大的组件。即使使用这些极端的温度设定值，也很少观察到部件上的可见缺陷。在进行横截面分析时，在通孔接头中观察到圆角抬升现象。定期分析焊料成分。特别注意铜或铅含量可能增加的问题。SAC合金浸出印刷电路板铜的速度比锡铅焊料快。从多氯联苯中溶解的铜增加了焊料中的铜含量。测试系列包含部分带有锡铅端接元件的电子组件。锡铅端接元件可能是无铅焊料铅污染的来源。如果将受铅污染的工具用于焊料罐维护，如清除渣土，也会带来严重的铅污染风险。分析显示，在测试系列中，铜或铅的含量没有显著增加，可能是因为与生产量相比，焊接的多氯联苯的数量较低。
Test series with different wave soldering parameters were run to examine the solder quality achieved in a lead-free wave soldering process. The solder was a Sn -Ag-Cu (SAC) alloy. Solder pot temperature was set between 250°C and 275°C. The most often used pot temperature was 260°C, which is the pot temperature usually used with SAC solders. Other examined process parameters were the solder contact time, soldering atmosphere, preheating temperatures, flux type and flux amount. The test series included different lead-free PCB finishes. Solder bridges and unsoldered SMD components were often observed likely due to the higher surface tension of the SAC alloy. By optimizing the soldering process the amount of these defects can be minimized. One of the main problems observed in lead-free wave soldering was the difficulty to solder through-hole components with a large thermal mass. Typically components with a large thermal mass could be soldered only with long solder contact times and high solder temperatures. Visible defects on the components were rarely observed, even when using these extreme thermal set values. Fillet lifting phenomenona was observed in the through-hole joints when cross sectional analysis was accomplished. Solder composition was analyzed regularly. Special attention was paid to possible increase in copper or lead content. SAC alloys leach PCB copper faster than tin-lead solder. Copper dissolved from PCBs increases the copper content in a solder. The test series contained partly electronics assemblies with tin-lead terminated components. Tin-lead terminated components are a possible source of lead contamination of lead -free solder. A significant risk to lead contamination is posed also if lead contaminated tools are used in solder pot maintenance, like in removing dross. Analyses revealed no significant increase in copper or lead content during the test series, probably because the amount of soldered PCBs was low compared to production volumes.