Printed Circuit Board industry is evolving as new production technologies become available at low cost. Direct digital printing is making inroads into the traditional photolithography and screen printing processes that have been used to manufacture PCB for the last twenty years.

Here we will focus on the use of direct digital printing to individualize PCBs just prior to their assembly. The goal is to print a unique mark on each board that can be used to identify the board. The mark must be permanent and will probably contain 1D or 2D machine readable codes along with alpha numeric characters. The marks must have a 600 DPI (dots per inch) resolution or better due to size constraints on the PCB. We will also focus on applications that require more that 1,000,000 boards per year. At these volumes automated material handling starts to become very important to the overall success of the system.

High volume PCB fabrication use screen printing with thermally cured ink to print the legends that cover each side of the board. At this time digital printing can not print the whole side of a board at a price that competes with screen printing. Even though many printers, including the PPS7000, could print all the nomenclature on the board, here we will focus on using digital printing only to print the individualizing marks.

Several individualizing options exist including the following:

1.Preprinted Label Application

Many low volume products start with labels printed on office equipment and hand applied to each PCB prior to or after assembly. As the product volumes ramp the reliability and cost of hand applying labels becomes a problem. Automated systems that print and apply labels are available. (see this site ) Because of PCB space constraints these systems must place labels very accurately, a big problem for many label application systems. The labels are not permanent. At high volumes the labels are more expensive than other marking methods.

Advantages

Low Initial Cost
High Contrast Mark

Disadvantages

Not Permanent
Higher Incremental Cost
Difficult to Change Label Size On The Fly
Mechanical Complexity For Automated Application

2.Solvent Based Continuous Ink Jet Digital Printing

Continuous ink-jet technology has been adapted to mark on many industrial products including PCBs. With these systems a continuous stream of ink droplets is steered to the desired location using electromagnetic fields. Solvent based inks produce permanent marks on porous surfaces. The marks are less permanent on non-porous surfaces where smearing may be a problem for the short time its takes to dry.