The pcba board industry is evolving as new production technologies become available at lower cost. Direct digital printing is making inroads into the traditional photolithography and screen printing processes that have been used to make PCBs for the past twenty years.
Here we will focus on using direct digital printing to individualize PCBs just prior to assembly. The goal is to print a unique marking on each board that can be used to identify the board. The mark must be permanent and possibly consist of alphanumeric characters with 1D or 2D machine-readable codes. Marks must have a resolution of 600 DPI (dots per inch) or higher due to printed circuit board size limitations. We will also focus on applications that require more than 1,000,000 boards per year. With these volumes, automated material handling is becoming critical to the overall success of the system.
High-volume PCB manufacturers use thermally cured ink screen printing to print legends covering each side of the board. Right now, digital printing can't print an entire board at a cost that competes with screen printing. Although many printers, including the PPS7000, can print all the names on the board, here we will focus on using digital printing to print individual signs.
There are several customization options, including the following:
Application of pre-printed labels
Many low-volume products start with labels printed on office equipment and hand-applied to each PCB before or after assembly. As product volume increases, the reliability and cost of manual label application becomes an issue. Automated systems are available that print and apply labels. (See this site) Due to limited PCB space, these systems must place labels very precisely, a major problem for many label application systems. Labels are not permanent. At higher volumes, tags are more expensive than other marking methods.
Benefit
Low starting price
High contrast branding
Disadvantages
Not permanent
High additional cost
Changing the label size on the fly is difficult.
Mechanical complexity for automated applications
Solvent-based continuous inkjet digital printing
Continuous inkjet technology has been adapted to mark many industrial products, including PCBs. With these systems, a continuous stream of ink droplets is directed to the desired location using electromagnetic fields. Solvent-based inks produce permanent marks on porous surfaces. Marks are less permanent on non-porous surfaces where staining can be a problem due to shorter drying times.
Benefit
Competitive extra cost
High contrast branding
Many colors are available
Disadvantages
The complex process of ink viscosity can be difficult to control
Having trouble getting high resolution (over 300 DPI)?
Solvents can be released into the atmosphere, many companies are trying to reduce solvent problems.
Mark not resistant to some cleaning solvents.