What factors are related to voids in smt solder paste mounting

With the improvement of high-end materials and processes nowadays, as well asPCBThe design and chip manufacturing capabilities are getting higher and higher, the volume and size of circuit boards are getting smaller and smaller, but their functions are increasing. Then the coreBGA,QFNIt is constantly increasing on the circuit board. Then insmtThere will be a large number of quality issues in the surface mount technology (SMT) stage. Now, let's take a look at Shenzhen JJYSolder paste manufacturerLet me explain:

1,PCBThe surface mirror layer.PCBThe influence of the surface layer on voids is mainly related to wettability. The better the wettability, the fewer the voids. Generally, the general tendency for the coating to produce voids isOSP(The largest)＞Non-precious metals＞Precious metals(The smallest).SmtIt is usually more effective for processing plants to reduce voids by improving wettability than by increasing the flux's soldering capacity.

There is another special case, that isIm-AgThe coating, although it is a precious metal, is also prone to voids, which is related to the presence of organic substances in the coating. Usually,Im-AgThe coating may contain30％The organic impurities, as shown in the above picture, when the coating is thin to0.2um(0.8mil)At this time, silver will dissolve into the solder within a few tenths of a second, and there are basically no organic residues in the solder joints during the surface mount processing. However, if the coating is relatively thick, the solder will not be completely dissolved. During reflow soldering, the organic impurities remaining in the silver coating will decompose and release gas, forming a dense interface vowel phenomenon, namely the champagne vowel

2,PCBThe typical definition of solder mask is the voids caused by the solder pad and blind hole. The formation of voids can be due to the evaporation of closed air or residual organic impurities.

3The larger the area of the solder joint and the width of the pin, the higher the cavity.

The above is an introduction to some issues related to voids. If you need to know more about our products, welcome to follow JJY Solder Paste Factory and leave an online message to interact with us.