The template, also known as steel screen and wire screen, is used to quantitatively distribute solder paste or adhesive glue, and is the key tool for ensuring printed circuit boards. The main methods of template processing are Chem-Etched, also known as chemical etching, laser cut, hybrid, Electroformed. Each processing method has unique advantages and disadvantages. Chemical etching is a substractive process, laser cutting is a mechanical processing method, and electroforming is an incremental process.
Generally, when the lead pitch is 0.025in or more, the chemical etching template is selected to achieve the same printing effect as other technologies. When the pin pitch of the pcb board is below 0.020in, the template for laser cutting and electroforming should be considered.
Another technique for improving solder paste release for pitches below 0.020 in. is a trapezoidal cross-section opening with the flare down, as shown in Figure 1. The solder paste deposit obtained by the trapezoidal cross-section holes is in the shape of a trapezoidal "brick". As shown in Fig. 2, the trapezoidal "brick" shape of the solder paste deposition pattern is advantageous for stabilizing the pcb mounting and producing less solder joint bridging.