The assembly of electronic boards (PCB) has a key step, the application of soldering paste in order to solder SMDs. This is a comparative overview of the available solutions, as well as some trends to help you anticipate changes.
Soldering paste, or brazing paste, is composed of a “brazing flux” or viscous solder flux (colophane for example) in which a metal powder has been put into suspension. The use of soldering paste has advantages compared to the use of soldering metal.
Three technologies are used to apply the soldering paste to an electronic board: syringe application and Jetting are the serial methods (one spot at a time), whereas screen printing is a parallel method (all the points at the same time)
Based on your requirements we can explore these options depending on the size of the production run and the complexity of the product.
By applying the soldering paste using a syringe, the dosing system manages either the pressure and opening time on a distribution valve, or the volume (using a worm screw). The dosing system is called the “Dispensing system”.
Up to a few hundred boards, Jetting is an excellent option. Using a principle similar to ink jet digital printing, Jetting directly applies the soldering paste to all types of electronic board, even if they have already been assembled. This recent solution is gaining ground thanks to its attractive advantages.
• Jetting is quick and not costly to implement; there is no need for tools specific to the product being manufactured, you just need to create the printing programme
• There is almost no cleaning involved.
The determining advantage of screen printing is the printing cycle: once the stencil is in place, applying the soldering paste using a scraper is very quick.
Proto-electronics has chosen screen printing as it provides the necessary flexibility required for the parallel production of many manufacturing orders.
This is needed to meet the short deadlines our company offers for electronic board prototypes.
We would like to thank Philippe ALLARD (GEMIDO) and Alain MILLARD (Laser Technologie France) for their contribution.