One stop pcb assembly with pcb stencil for usb charger

Now, boards with no components assembled on the surface of board are called bare boards. More than four decades ago, soldermask didn't exist and copper lines were exposed to the air. Put in another way, this type of finished PCB is actually an exposed bare board. In this stage, components were assembled on PCB through lead plug-in soldering. Pad of PCB is a copper surface and solder wire with rosin core is applied to be soldered by soldering iron. Later, flux is coated on the whole PCB surface in order to protect circuit and solder pad and the coating method is mostly through flux of rosin and resin spraying. Of course, chemical silver plating is applied sometimes.