Recently, Eurocircuits introduced a spray coating process for Soldermask, this brings many advantages including a thinner and more unified coating which helps us to meet today’s technology challenges.

The Soldermask is imaged using a Dai Nippon Ledia Direct Imaging system; this improves registration accuracy and eliminates the need for Photo-tools.

The spray coating of Soldermask is only achievable due to the low viscosity of the ink. Due to this low viscosity however, there may also be Soldermask ink in the barrel of the Via Hole. This may or may not remain after final curing depending upon the data provided by the customer.

To avoid any potential issues we always open all holes (NPTH, PTH and Via Holes) to be free of Soldermask unless the Via Holes are filled and have no Soldermask opening defined.

The Soldermask data we receive for Via’s (holes and pads) varies from customer to customer, the Via’s may have no Soldermask Opening, meaning they are to be completely covered with Soldermask, also known as Tented Via’s (see our PCB Design Guideline – Soldermask Tented Via Holes section).

Fully Tented Via Holes with spray coating is only possible in conjunction with Via Filling due to the viscosity of the ink.

If the data shows untented Via Holes or Pads we follow our standard design rules, as below:

Minimum Soldermask Opening of 0.4mm

Additionally, we ensure that our other design rules for Soldermask are also met, as below:

  • MAR (Mask Annular Ring) – the clearance between the Soldermask and the copper pad.
  • MSM (Mask SegMent) – the bridge of Soldermask between adjacent pads.
  • MOC (Mask Overlap Clearance) – Soldermask coverage between a track or plane and an adjacent Soldermask Opening.