Before introducing the PCB design opening, we first need to know what the solder mask layer is. Solder mask layer is the part of the PCB board to be inked, used to cover the alignment and lay copper to protect the metal elements on the PCB and prevent short circuits. Solder mask opening is an opening in the solder mask layer for soldering at the location of the opening, simply put, the opening is not covered with ink location. Any location without printed solder mask can be called opening, not printed solder mask location are solder pads, SMD PAD, digging slot location, etc.. There is also a situation called half opening, half opening is the part of the pad is not covered with solder mask film, part of the cover solder mask film.
How to distinguish between “Via hole with opening” and “Via hole solder mask”?
In the PCB design may often hear the “Via hole with window” and “Via hole solder mask” these two terminology. In fact, they are the literal meaning, opening on the hole, a hole cover oil. In other words, whether to insulate the surface of the PCB.
Opening means that in the opening position can be easily on the tin, can be judged according to whether the tin can be on the opening. Cover oil, means that it is not easy to tin when the patch, which is the process decision. Why will appear over the hole feel no cover oil reasons are as follows: because the solder mask oil is liquid, over the hole in the middle and empty, in the solder mask ring on the solder mask oil after baking process is easy to oil into the hole, which leads to over the hole yellowing situation occurs, this situation by the concentration of solder mask oil, baking oven and with strength, so there will be some above can appear green, and some can not appear the situation.
Why need a solder mask opening?
For via hole, the ink of solder mask layer will enter the hole if no opening is done. For some holes that do not require ink plugging, it is necessary to design it as an over-hole opening. For through-hole mounted components, if the PCB is not solder mask opening, the components will not be properly soldered to the board. Hole openings are not only only convenient for soldering this function, but also can be measured on the through-hole. For some special location of the hole for solder mask opening, you can use a multi-meter on the through-hole measurement.
For PCB, if not make a solder mask opening,It will not be possible to do surface treatment, spraying tin and soldering.
How to make a solder mask opening?
1, The PAD in the PCB design by default will opening(OVERRIDE: 0.1016mm), that is, the pad exposed copper foil, the outer extension of 0.1016 mm, wave soldering and tinning. It is recommended not to make design changes to ensure solder ability.
2, Via hole in the PCB design by default will opening (OVERRIDE: 0.1016mm), that is, over-hole exposed copper foil, external expansion of 0.1016 mm, wave soldering on tin. If the design is used to prevent over-hole tinning and does not expose copper, you must check the PENTING option in the additional properties of the via-hole SOLDER MASK to close the via-hole.
3, In addition this layer can also be used alone for non-electrical wiring, the solder mask green oil corresponding opening. If it is on top of the copper foil alignment, it is used to enhance the over-current capability of the alignment, when soldering, can be tinned. If it is on top of the non-copper foil alignment, it is usually designed to do logo and special character screen printing, which can save production.