The most common defects in reflow soldering of SMT

 Abstract: The quality of SMT reflow soldering is affected by many factors. The most important factor is the temperature profile of the reflow oven and the composition of the solder paste during the electronic production process. Here are the most common 17 kinds of reflow soldering defects.

Common defects of SMT reflow soldering

(1) Incomplete melting of solder paste-there is unmelted residual solder paste around all or part of the solder joints.

(2) Poor wetting-also is known as non-wetting or semi-wetting. The solder ends of the components, pins or printed circuit board pads are not wetted or partially not soldered.

(3) Insufficient amount of material and false welding or open circuit-the height of the solder joint does not meet the specified requirements, which will affect the mechanical strength of the solder joint and the reliability of the connection. In severe cases, it will cause false welding or open circuit.

(4) Bridge and displacement-suspension bridge refers to the surface-mounted components with two solder end. After reflow soldering, one of the ends leaves the surface of the pad, and the entire component is inclined or upright, like a stone monument. It is also called the tombstone phenomenon, Manhattan phenomenon; displacement refers to the phenomenon of dislocation of component ends or pins away from the pads.

(5) Solder point bridge connection or short-circuit-bridging is also called bridging. Between the ends of the components, between the adjacent solder joints of the components, and between the solder joints and adjacent wires, the parts that should not be connected electrically such as national control are welded together (the bridge is not necessarily short-circuited, but the short-circuit must be bridged. even)

common defects in reflow soldering

(6) Solder ball-also known as a solder ball, solder ball, refers to the tiny beads of solder scattered around the solder joints.

Solder ball

(7) Air holes-air holes, pinholes, or voids distributed on the surface or inside of the solder joints.

(8) The height of the solder joints touches or exceeds the component body, and the phenomenon of material absorption-the solder moves to the solder end or the root of the pin during soldering, so that the solder highly touches the component or exceeds the component body.

(9) Tin wire-Tiny tin wire between component soldering ends, between pins, soldering ends or between pins and through holes.

(10) Element cracks and defects-there are different degrees of cracks or defects in the body or end of the element.

(11) Peeling off the coating on the component tip-the electrode coating on the component tip is peeled off to varying degrees, exposing the component body material.

(12) Components stand sideways.

(13) The component side is stuck on the reverse side-the character of the chip resistor is facing down.

(14) Cold welding-also known as solder disorder. There are traces of solder disorder on the surface of the solder joints.

(15) Solder cracks-there are cracks on the surface or inside of the solder.

(16) A section of the tombstone-chip component is lifted and standing on the pin at the other end is also known as the Manhattan phenomenon or suspension bridge.

A section of the tombstone

(17) Other

There are also some defects that are invisible to the naked eye, such as the grain size of the solder joint, the internal stress of the solder joint, and the internal crack of the solder joint. These can only be detected by X-ray, solder joint fatigue test and other methods.

These defects are mainly related to the temperature profile.

For example, if the cooling rate is too slow, large crystalline particles will be formed, resulting in poor solder joint fatigue. If the cooling rate is too fast, it is easy to produce component body and solder joint cracks; For example, if the peak temperature is too low or the reflow time is too short, it will cause problems. The phenomenon of fusion replenishment and cold welding, but the peak temperature is too high or the reflow time is too long, it will increase the production of common boundary metal compounds, make the solder joints brittle, and affect the strength of the solder joints. If 235℃ is over, it will also cause The epoxy resin in the PCB fabrication is carbonized, which affects the performance and life of the PCB.

The above are the common reflow soldering defects of SMT reflow soldering by Kingford. Hope it will be helpful for you. If you have any questions, please feel free to contact us:sales@kingfordpcb.com.

评论

发表评论

此博客中的热门博文

How to generate BOM and Pick and Place File in Proteus

图片
  In this tutorial, let’s see how to generate BOM (Bill of Materials) and CPL (Component Placement List) in Proteus. This tutorial was written for Proteus 8.13 version and the "dsPIC33_REC " sample project shipped with Proteus is used. Generating the BOM 1. First, click the Bill of Materials icon (the Dollar sign icon) on the toolbar and the Bill of Materials tab will show up. Figure 1.Proteus BOM Icon Figure 2.Bom list 2. It’s time to generate the BOM. Menu operation: Generate → CSV Figure 3.Export Bom Generating the Pick and Place File 1.First, switch to PCB Layout Tab and click the Toggle Metric/Imperial icon to change the unit to metric.  Figure 4. Switch to Metric 2.Execute Output → Generate Pick and Place File Figure 5. Generate Pick and Place File Menu Operation 3.Export to CSV file and save
阅读全文

Understand the Basics of SMT Assembly Process: SMT Assembly Components

图片
  What is SMT? Surface Mount Technology is a space of electronic used to mount electronic segments to the outside of the PCB as go against to embedding parts through-hole similarly as with regular gathering. SMT was created to diminish producing expenses and furthermore to utilize PCB space. What is SMT assembly? The Basics Surface mounting is an approach to deliver electronic circuits by setting parts straightforwardly onto the board’s surface.  SMT assembly  is an option in contrast to the through- technique for PCB fabricating, which had its prime during the 1970s and 1980s.   What is SMT in manufacturing? Gadgets fabricating utilizing surface-mount technology (SMT) basically implies that electronic segments are gathered with computerized machines that place parts on the outside of a board. With regards to electronic get-togethers, SMT is the most habitually utilized cycle in the business.   What is SMD? Surface mount device or SMD is the term utilized for th...
阅读全文

PCB 电子线路板制作流程

  有幸参观过电脑主板的制作流水线，一共几十道工序，与一般的产品生产要求不同， PCB制造 业对员工健康要求较高，从事这个行业的一线生产的员工的健康状况让人担忧。由此想到自己坐在明亮的办公室，真应该少一些抱怨，多做点实事。 流程大致如下 1  开料 把买回来的铜片，像纸一样的，一卷一卷的，切割成不同大小尺寸的小铜片。 2  内印 内层线路版印刷，把PCB板的内层线路印刷到开料的铜片上。 3  压合 经过上一道工序，有了 内层线路版 ，为了保护这层线路，需要在它的正反面压上一层材料，防止张线路被破坏。材料的名字不记得。 4 钻孔 当我们打开机箱，看到电脑主板上有很多电子无件，这些元件需要有孔才能固定在板上，这一道工序在板上打孔，就像平时我们看到修路工人用机器在地上钻孔一样。打孔机的针头依磨损的部件，公司每年要花一笔费用于于更换损坏的针头。 5 PTH 在孔里面渡铜(Cu). 作用很明显，刚打出的孔可能会被后来的工序损坏，铜的承受力比较大，保护这些孔。为什么不渡其它的元素呢，这里面有学问，不是一句两句可以说明白的，后面还有渡锌的工序。 6 外线 终于可以进行外层线路版的印刷。 7 电镀 渡上一层锡，蚀刻。具体内容记不清了。 8 半测 这里就开始半成品的测试，发现内线有问题的，要及时修复，有的客户要求有问题的不允许修复，直接报废。报废后这块板上有铜料，可以回收（用化学反应提取出来）。 9  防焊 10 喷锡 11 文字 根据客户的要求，在板上刻上文字。现代生产中，OEM生产很普遍，通常是用油墨把客户要求的文字印在板上，然后到高温烤房里面烤干。 12 成型 13 成测  成品测试 14 成检  成品检验 最后会有几道工序检验这块板是否可以使用。如电脑没有pass,要被送到指定的位置通过人工的方式修复，做这个工序的需要耐心，所以那里的员工通常是女孩子。 15 包装 16 出贷 生产流程写完了，写点题外话 1 如果你化学成绩很好，在这种厂干，最适合你发挥聪明才智。我见过一个员工，他的工作就是在实验室的配置药水，穿着像医生一样，白大褂。 化学分子式铜Cu, 水H2O,双氧水HO2,盐酸HCL,硫酸H2SO4, 硝酸HNO3, 石灰水Ca(OH)2 在读初中的时候学过，朋友，你还记得多少呢？ 2 PCB板的生产是流...
阅读全文