In electronic design automation, the solder mask is treated as a layer of the printed circuit board and is described as a Gerber file like any other layer, such as the copper and silkscreen layers. All three processes typically go through a thermal cure of some type after the pattern is defined although LPI solder masks are also available in the ultraviolet (UV) cure. DFSM is vacuum-laminated on the PCB then exposed and developed. LPSM can be silkscreened or sprayed on the PCB, exposed to the pattern and developed to provide openings in the pattern for parts to be soldered to the copper pads. Other types are the liquid photoimageable solder mask (LPSM or LPI) inks and dry-film photoimageable solder mask (DFSM). The lowest-cost solder mask is an epoxy liquid that is silkscreened through the pattern onto the PCB. Solder mask comes in different media depending upon the demands of the application. Solder mask is traditionally green but is now available in many colors. Once applied, openings must be made in the solder mask wherever components are soldered, which is accomplished using photolithography. Solder mask is not always used for hand-soldered assemblies but is essential for mass-produced boards that are soldered automatically using reflow or Wave Solder techniques. PCBs use solder masks to prevent this from happening. A solder bridge is an unintended electrical connection between two conductors using a small blob of solder. Next the board is preheated, and finally the solder head follows the programmed route to solder the connections.Solder mask or solder stop mask or solder resist is a thin lacquer-like layer of polymer that is usually applied to the copper traces of a printed circuit board (PCB) for protection against oxidation and to prevent solder bridges from forming between closely spaced solder pads. When the program is loaded and the solder pot is heated, the boards enter the machine from a conveyor, and the soldering process starts once the board reaches its destination.įirst the machine sprays flux on the selected area. We can adjust the distance of the head to the board and the soldering speed to get a good solder quality. We program the machine with simple point and click programming.Ī canvas with the image of the bottom side of the board is loaded, and we indicate the points and route the flux sprayer and solder head need to follow. The equipment we use is an Ersa Ecoselect 2 selective soldering system, perfectly suited for prototype and small batch production. Wave soldering works much faster, but the whole board is touched by high temperature molten solder.įor selective soldering, components do not need to be glued to the board when soldering, we use less flux and solder, and there is no need to cover parts of the board with a mask to prevent solder deposition or heat damage. Many components cannot be processed on wave soldering.Ī selective soldering machine uses a single head that moves to the point where solder needs to be applied, and leaves the rest of the board untouched. When there are components close to the point to be soldered, we risk damaging the component, or wash it off the board.Ĭompared to a solder wave selective soldering has some clear advantages. We don’t use the selective soldering equipment when component leads are too long ( 2 mm or more), because the solder head stays too far from the pads, and a good solder joint is not guaranteed.
#Pcb soldering manual#
Compared to manual soldering, this process is faster, repeatable and leads to a better result.Īs always this technology has limitations. The solder fountain or head moves to the position to solder from underneath. The machine includes a flux spray, preheater and a soldering pot that feeds a solder fountain. Selective soldering is a process to solder individual through-hole components on a PCB. Through hole components can be soldered manually, over a solder wave, or with a selective soldering machine or soldering robot.