Solder paste printing attaches surface mount devices to printed circuit boards. Over 70% of Surface Mount Technology defects are driven by solder problems.* The choice of solder paste can make a huge difference. As devices and their components become smaller, the solder connections are also correspondingly finer. Its hard to fill apertures for these small devices with coarser type 3 solder paste. Type 2 solder paste is almost never used on Printed Circuit Boards. Rather, it features in power and industrial products where the chip package is bigger.  

Until 2017, India had easy access only to type 3 solder paste which has 25-45 microns powder size. While it is possible to use type 3 solder paste for lead pitch between 0.3mm and 0.02mm , the reliability and durability of the boards reduces. Type 4 solder paste yields better results in our experience. We also use a Solder Paste Inspection system to ensure the right amount has been used.

Podrain has been sourcing and utilising type 4 solder paste, even though it entails a 20%-30% higher cost for the past 4 years. Now, we see an across the industry move to Type 4 solder paste  and even the manufacture of Type 3 solder paste is coming down. We are currently evaluating switching to type 5 solder paste which has a powder size of 15-25 microns for components that need to go on the smallest PCB’s. 

So when you are looking for a provider to make your PCBA’s, go beyond looking at the machines on the assembly line, and ask what solder paste is used. 

*Biemans. 2011. “5D solder paste inspection merits beyond 3D technology.” Global SMT and Packaging 8-13 

References: 

https://blog.gotopac.com/2020/03/13/solder-paste-types-powder-sizes-for-smt-dispensing/

https://scholarworks.rit.edu/cgi/viewcontent.cgi?article=10208&context=theses