First of all, we can say that a solder mask (soldering machine) is a protective layer in polymer fluid structure, obtained using various printing technologies used in the manufacturing process of a printed circuit board (PCB). It is the colored part of the PCB. Copper paths are formed as a result of copper etching process in PCB manufacturing. These paths are exposed to air and corroded. The copper paths are protected by applying a protective layer of solder mask on copper. This is basically a PCB manufacturing process that protects metal elements from oxidation and is applied to prevent formation of a bridge (short circuit) between solder pads. Due to this feature, it is also called “solder resist”. Solder mask can be produced in various colors such as green, red, blue, white, black, yellow. The most commonly used color is green. Methods such as Dry-Film and Liquid Photo-Imageable are used to process the solder mask to the PCB base. Solder mask bridge is the process of closing the feet of the integrated element and insulating the solder area by painting. Gerber files specify which regions of the solder mask layer will be covered. In practice, it is necessary to indicate that the region to be covered is the “negative part” of the data. In fact, the solder mask bridge appears as a result of the standard solder mask application. The “precision in manufacturing” is the main enabler of this concept. The main purpose is to prevent short circuits by creating a buffer zone between the feet of the integrated element. *Whether the solder mask bridge can be produced depends on the distance between the pads of the component (such as the integrated element, connector etc.), the color of the solder mask and the production technology used. For example, if the solder mask color is green and the copper value is 1 oz in standard PCB production, and the integrated element’s pad range is 0.20 mm, the manufacturer can produce a solder mask bridge. However, this is not possible if the pad range is shorther. Standardly, in order to make a solder bridge in blue solder mask a minimum of 0.25 mm is needed as the integrated element’s pad range, which means solder bridge cannot be produced if a blue solder mask is requested.
If the manufacturer’s capacity to produce a solder mask bridge is below these values but they still attempt to make a solder mask bridge, the Dry-Film method, especially, may cause the mask to slip during production. This slip can overlap the pads, causing the surface coating to deteriorate, and lead to a short circuit. In addition, it may cause a short circuit on the tin of integrated element’s pads during surface coating from PCB production processes. On the other hand, we cannot make a general assumption that a short circuit will necessarily occur when the solder mask bridge cannot be produced. The PCB placement is an integrated process, and there are many PCB production and string parameters, such as the screen thickness and the compatibility between screen eyelets and component pad structure to prevent a short circuit. As Özdisan PCB department, we contribute to product quality and manufacturing efficiency, by analyzing the risks associated with PCN manufacturing and placement and acting as a bridge between the PCM manufacturer and placement partner.
Bevelling
Bevelling is the process of cutting the PCB ends by bevelling. This process gives the edges of the board a pointed form so that it can fit into a socket. Chamfering is applied to the PCB edge with a certain angle by using a cutting tool. Although bevelling causes extra costs for PCB manufacturing, it makes it easy to install the PCB when used as a connector. This process is especially used in applications such as memory cards in a computer and allows the memory card to fit on the motherboard more easily. In general, it helps to create external connections in industrial applications.
Black Hole
Black Hole is the process of metallizing the boreholes on doublelayer PCBs. A carbon-based nanoscale electrostatic coating is used to provide conductivity. We can compare this with PTH coating to better understand the process. In PTH coating, copper coating is carried out using current, while in the Black Hole method the boreholes are metallized by carbon impregnation. The advantage of this method, which is cheaper compared to PTH coating, is that it offers faster production. However, the thickness of the borehole metal coating is smaller when compared to PTH coating. Black Hole is not used in Multilayer PCBs. It is not preferred for 2 layer PCBs since the performance quality is low.
