PCB Tech - Speed and throughput of next-generation PCB printers

In the simplest description, faster PCB printers logically mean higher throughput. However, the overall speed depends on many factors, including the cycle time of each step in the printing cycle (for example: stencil wiping frequency, substrate separation speed, and printing speed). The overall throughput speed of the stencil printer, that is, the speed of printing each board, must match the capacity of the production line. In other words, if the production line speed is determined by the reflow oven at the end of the production line, and the fixed time/temperature curve is obviously slower, then the fast printing machine and/or high-speed placement machine will not bring any benefits. The configuration and balance of the production line should be optimized from the entire production line. Therefore, PCB printers capable of high-speed mass production are only an important part of achieving maximum benefits.

The benefits of higher throughput

The configuration and balance of the production line is an important part of each process of the production line to achieve maximum benefits, from the material handling system (buffer, board loading and unloading machine, etc.) to the operation of various process equipment. A printing press with high throughput is theoretically "fast"; mechanical systems, software, frame stability, motion control and sequencing, all of which have an impact on each device. With a comprehensive understanding of the throughput capacity of the printing press, production engineers can use the advantages of each device with maximum flexibility in any number of production line settings, configurations or scenarios. A single printing machine has enough throughput to cope with two production lines, so as to be fully utilized and save equipment investment. If you buy two printing presses for two production lines, neither of the two printing presses will be fully utilized.

When we talk about "speed", what we really want to talk about is "throughput", that is, the time it takes for a PCB to enter the printer, print, and exit the printer. This is different from "cycle" time. The total throughput is the sum of the cycle time of this process, including processes such as printing stroke, stencil wiping, PCB sorting, and alignment. Some cycle times can be shortened; some cannot, such as the printing stroke, it will have an optimal speed (usually not exceeding) depending on the type of solder paste used, the template, the size of the template opening, etc. Higher throughput supports mass production and processes.

With higher speed, you can now:

Printing at a slower speed;

For the best printing resolution, use a low template separation speed;

Wipe more frequently with the MPM Edison high-efficiency wiper (if necessary);

The precision printing doubles after wiping.

Have time to optimize the settings to provide the greatest possible rate of return!

What is a "fast" press?

The speed and throughput of next-generation printing presses. The mechanical system, software, frame stability, motion control and sequencing of the printing press all have an impact on the overall operating speed of a single device. The "total throughput" time is the time from when the PCB is guided into the device until it exits the device, and is the true measurement speed. For example, a device with a total throughput time of 15 s will be considered a fast device. The total throughput time is the sum of the time of the equipment holding and each process of the printed substrate, that is, the accumulation of the cycle time of each process such as alignment, printing stroke, stencil bottom wiping, and substrate guidance.

Only speeding up the printing stroke, that is, the moving speed of the scraper on the template, is not an option. According to different applications, such as fine pitch or standard pitch, the size and shape of the openings, the thixotropy of solder paste, etc., each application will have an "ideal" printing speed to obtain the highest yield while eliminating solder paste. Defectively transferred to PCB. A good printing effect is that the solder paste rolls in front of the squeegee and completely fills the stencil opening under a certain pressure. A printing stroke that is too fast will cause insufficient filling of the openings, and will accelerate the collapse of the solder paste viscosity through shearing. Therefore, an ideal printing stroke speed requires a printing stroke that lasts several seconds, and shortening the entire printing cycle time will have to be considered in other aspects.

period time

PCB printing involves multiple processes, but not every process is part of every PCB printing process. For example, the template wiping process with an automatic wiping system is like this. The manufacturing process engineer can choose to set the wiper to wipe once every ten substrates or once every three substrates. This depends on many factors, but ultimately depends on the overflow of solder paste around the openings at the bottom of the template. Obviously, process engineers want to minimize the frequency of wiping, because wiping also takes up throughput time, as well as the cost of solder paste loss. Changes in the printing process such as solder paste type, viscosity, stencil opening size, substrate topography and sealing, etc. all affect the wiping frequency. When needed, depending on the type of wiping system used, there is a specific wiping cycle interval time. This cycle time must be added to such as PCB alignment, substrate operation, solder paste replenishment, printing strokes, etc., to establish or calculate the "real" throughput Amount or speed. For example, the newly released MPM Edison printer platform achieves an average throughput speed of 15 s per printed substrate, including printing strokes and stencil wiping; due to lower stencil wiping frequency requirements, the average printing time is further shortened.

15 s throughput calculation

Of course, each application will have a different throughput speed, which depends on a number of factors, including (especially) the type of solder paste used, the size of the PCB, the size of the template opening, and other variables. Therefore, the time required for the new MPM Edison printer to reach 15 s is determined by whether it uses a standard board or an ordinary board and the printing procedure, which will be the benchmark for most PCB printing schemes. The throughput of 15 s is achieved under the following parameters, including printing stroke and wiping stroke