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July, 2021
Practical Jet Printing with Modular Dispensing Systems
By Patrick Miron, Mechanical Engineer, VERMES Microdispensing America, Inc.
for a complete circuit assembly has brought production levels of SMT to an all-time high. To achieve this, screen printing has become the most common method of applying solder paste. But, screen printing has some draw- backs, namely wasted solder paste, wasted floor space due to large machine footprints and stor- age space for stencils and their organization. And, if a substrate is not flat and has protrusions, screen printing cannot be used. VERMES Microdispensing
T
offers jet printing as a remedy. Jet printing can be directly inte- grated into pick-and-place mach - ines, solder inspection machines, or placed in a machine solely for dispensing. The technology of sol- der paste jetting has advanced greatly in the past two years, yielding the VERMES DST-based MDS 1560 jet printer which enables solder paste jetting with- out crushing solder balls.
The Cost of Speed Jet printing cannot hope to
compete with the pure speed of screen printing. However, there are some important considera-
he ability to quickly apply solder paste, pick and place circuit elements and reflow
tions for screen printing. First is the time and cost necessary to design, manufacture, store, and clean stencils that perform to expectations. Typically, a stencil can only
be used for one application. The apertures in the stencil are
spent in the process. Screen printing as a process
also incurs the loss of solder paste, as it involves applying a large amount of paste onto the stencil. Screen printing lower- cost solder paste makes this flaw less noticeable, as the loss of material can be made up for by the speed of the process. Specialized applications that call for more costly solder paste quickly makes screen printing very expensive. Jet printing can be used to dispense solder paste that can cost thousands of dol- lars per syringe, exactly where it is required without waste. Screen printers are expen-
MDS 1560 jet printer mounted inside an Essemtec Fox2 system.
specifically designed for one application, and once that appli- cation is finished, the stencil becomes useless. During their unique application, stencils must be regularly cleaned and main- tained, adding to the total time
sive machines with large foot- prints. SMT line screen printers are usually located prior to pick- and-place equipment. In some cases, buffer conveyors or buffer elevators are used to give the pick-and-place machine time to place circuit elements, as-pick and-place cannot match the speed of screen printing. Not only does this waste
both time and money, but the speed at which solder paste is dispensed, which is the main benefit of screen printing, often does not end up mattering because of this bottleneck.
Screen printing machines
often stand idle waiting for the other assembly processes to be completed. This can impact sol- der paste quality, and in the long term can be harmful to the machine.
Test board with jet printed solder.
Finally, screen printing can-
not be used on substrates that are not completely flat.
A Smaller Solution In stark contrast, jet print-
ing is less about speed and more about precision, accuracy and convenience. The first advantage that the VERMES MDS 1560 systems have over screen print- ers is their easy implementation into existing pick-and-place machines. A machine can be outfitted with component feeders, pick- Continued on next page
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