SMT chip refers to a series of processing processes based on PCB, and solder paste printing in SMT chip process is the first and most important step.
There are two ways of solder paste printing: screen printing and dispensing. Jiamei screen printing is mainly engaged in the production and sales of screen printing equipment. So we focus on PCB screen printing.
Screen printing: it is used to leak solder paste or patch adhesive onto PCB pad to prepare for component welding. The equipment used is screen printing machine (screen printing machine), which is located at the front end of SMT production line.
Solder paste is a kind of homogeneous mixture, which is composed of alloy welding powder, paste flux and some additives. It has certain viscosity and good thixotropy. It is a homogeneous and stable mixture. Under normal temperature, the solder paste can initially stick the electronic components to the fixed position. When the solder paste is heated to a certain temperature, with the volatilization of the solvent and some additives, and the melting of the alloy powder, the solder paste reflow makes the components to be welded interconnected with the solder pad to form a permanently connected solder joint after cooling.
In the process of silk screen printing, an important tool is SMT screen printing frame, which is composed of screen frame and template.
Mesh frame is a frame used to support steel mesh (SMT template), which is made of metal, wood or other materials. It can be divided into fixed type and adjustable type. The most commonly used one is the pneumatic net frame made of aluminum profile.
Stencil type: important printing quality variables include the accuracy and finish of the template hole wall. It is important to keep the proper aspect ratio of the width and thickness of the template. The recommended aspect ratio is 1.5. This is important to prevent blocking of the template.
At the same time, SMT screen frame has a series of professional operations to enhance the strength and ensure the smooth progress of screen printing in the production process, and there are many strict requirements and operations in the opening process of the template, we will talk about it next time.