stencil/printing machines for solder paste

There isn't going to be much worthwhile used equipment out there if you mean true jetting - it is a pretty recent process. There are lots of used stencil printers out there, so from an up-front cost perspective, stencil wins.

Jetting is slow. A high end jet printer might quote a million dots per second, which seems like a lot. But most to all of your pads will require multiple dots. A board we run in some quantity has 5000 paste apertures per side. If you figure on average each aperture will require 8 dots, that is 40,000 dots per board. So at best 25 boards per hour.

But wait, there's more! Just like you'll never hit the "rated" speed of a pick and place machine because real boards aren't infinitely simple and infinitely small, so too a jet printer. For a real world case, knock that number down by 50% to account for board transport, alignment, clamping, moving between components and the like. So 13 boards per hour. Now add inspection. 8?

With a high end machine, my cycle time with jetting would be seven minutes or so for this board.

But that doesn't matter if the printer isn't the bottleneck. This same board has 1500 components on it. So if my real pick and place capacity is less than 13,000 parts per hour, jetting does no harm from a throughput standpoint.

Printers run pretty much all the time, whereas pick and place needs replenishment and tweaking. So to get to a real 13,000 parts per hour, figure you need to be able to do a real 20,000 parts per hour when the machine is running the boards. A real 20,000 parts per hour takes a machine rated 30k to 40k, depending on the board and machine. If your line is rated this much or more, jetting WILL slow you down. But low volume high mix suggests to me that it isn't.

The upside to jetting, of course, is no stencils. On the low end, that means faster turnaround time, faster setup and less storage. Also no stencil cost.

If you run some sort of automated prototyping line with a standard component database, jet printing would be wonderful. If you have package on package issues or very small and very large parts, jetting makes a ton of sense to augment post stencil print. As your only printer for general purpose use, though? No thanks.

reply »

Hi Sir, I would like advice for you SJ INNOTECH Screen printer Please reffer website : http://sjinnotech.com/ht_ml/main/ Many thanks for your information

reply »