Inkjet Printing of Solder mask

The future of solder mask is digital

Digital inkjet printing for the application of solder mask on PCB boards has a large number of significant benefits. Therefore PCB manufacturers and material suppliers are transitioning towards direct printed solder mask.

Simplified process flow

When comparing the traditional solder mask process with the inkjet based process, the largest benefit becomes apparent immediately. The traditional process contains pre-treatment, full board coating (often curtain coating), artwork film production, exposure, development and finally a post-cure step to reach required material hardness.

With inkjet this process can be reduced to only three steps. Pre-treatment remains a crucial step for good adhesion. Secondly the inkjet printer applies the solder mask material and uses UV curing so the boards come out tack free. The process is then concluded with a post-cure step.

It is obvious that this reduction in processes saves on capital equipment, labor on every process step, process chemicals and waste, and reduces handling and the buildup of yield problems. Moreover, it reduces the total time to finish a PCB board – an important asset in today’s fast moving electronics business.

Unique characteristics of inkjet

Additionally, inkjet technology adds a number of strong advantages. To begin with, inkjet is a selective coating technology. This means that material is only deposited where it is needed, not only reducing material consumption, but also avoiding solder mask material in holes and other areas where it is difficult to remove. Flushing uncured solder mask material from high aspect ratio holes in the development step is a known challenge in the PCB industry and is totally circumvented by inkjet printing. Secondly, by omitting the development step, there is no risk of removing small solder dams between IC contacts in this step.

Thirdly, inkjet is a very flexible process. It allows different surface finishes, different layer thicknesses and different materials. And finally, inkjet has the ability to accurately align and scale the print image to the board.

PiXDRO technology

The PiXDRO JETx-SMP inkjet production equipment is specifically designed for printing solder resist on printed circuit boards. This system enables fast and cost effective manufacturing of solder mask layers.

The JETx-SMP printer produces solder mask layers with the following specifications.

  • Line-Space: 75-75 µm
  • Edge roughness: 20 µm
  • Solder mask openings: down to 100 µm
  • >10 µm solder mask thickness on copper
  • Layer thickness: 30-80 µm, can be varied over the board to reduce material consumption
  • Alignment accuracy: <2 µm using automated fiducial alignment
  • Compatible with Taiyo and Agfa solder mask materials
 

Literature

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