3D printed solder masks for printed circuit boards

The use of additive technologies in the creation of soldering masks opens up new opportunities in the production of printed circuit boards, in particular, the use of soldering masks for boards with integrated components. The paper considers the results of experimental data on the adhesion of 3D soldering masks (that is, masks created on a 3D printer) obtained during the study of the introduction of 3D printing into electronic manufacturing processes. For the analysis of adhesion, it is possible to use such methods as breaking load, cross-cut test, and the sticky tape method. A number of experiments were conducted to study the adhesion by testing the breaking load. The samples were formed with different ratios of prepreg/solder mask, then the force at which the fracture occurred was measured. The essence of the cross-cut test is to apply at least three parallel cuts and perpendicular to them also at least three parallel cuts with the tip of the cutter. After the scratching, there must be no flaking of the coating between the lines and in the grid of squares, then the results are assessed. Sticky tape tests are performed by applying the tape with the adhesive side to the test sample with a cured coating applied. The results are assessed by visual inspection using an optical device that provides 3x magnification. The results of the breaking load experiments indicate that 3D masks show comparable separation forces with a prepreg. At the same time, the force is stable for all types of surfaces and practically does not depend on the thickness and configuration of the 3D mask. Experiments with applying cross-cuts show consistently good results with a homogeneous base material – there are no coating detachments. The paper concludes that the use of 3D soldering masks on the inner layers of multilayer printed circuit boards with built-in components is possible, but a number of issues must be solved for this, including those related to the software for forming 3D structures of masks.