Knowledge of Surface Mount Technology
1. Surface Mount Technology, SMT (Surface Mount Technology) what is the SMT: generally refers to the chip with automatic assembly equipment, the miniaturization of leadless or short lead Surface Mount component/device (hereinafter referred to as SMC/SMD, often called flake components), directly welded to the Surface of a printed circuit board (PCB) or other substrate Surface position of a kind of electronic Technology, also known as Surface Mount Technology or surface-mount Technology, hereinafter referred to as SMT (Surface Mount Technology).
2. Features of SMT:
The volume and weight of SMT component is only about 1/10 of that of traditional cartridge component. After SMT is generally adopted, the volume of electronic product is reduced by 40%~60% and the weight is reduced by 60%~80%.
High reliability, strong vibration resistance and low defect rate.
The high frequency features are good and reduce electromagnetic and rf interference.
It is easy to realize automation and improve productivity.
Save materials, energy, equipment, manpower, time, etc.
3. Classification of surface mounting methods:
According to the process of SMT, SMT is divided into point glue process (wave solder) and solder paste process (reflow solder).
The main differences are:
The process before the tape is different, the former USES the patch adhesive, the latter USES solder paste.
The technology is different after lamination. The former reflow furnace only solidifies the glue, plays the role of pasting the components to the PCB board, and also needs wave welding.The latter plays a welding role through the backflow furnace.
4. According to the process of SMT, it can be divided into the following types: single-side mounting process, double-side mounting process and double-side mixing process
Only surface mount components are used
A. Single-side assembly with surface mounting only (single-side mounting technology)
Process: screen printing solder paste, mounting component, reflow soldering
B. Double-sided mounting with surface mounting only (double-sided mounting process)
Process: screen solder paste – patch component – backflow solder – reverse – screen solder – patch component – backflow solder
A combination of surface-mount components on one side of the face and a combination of surface-mount components and perforated components on the other side of the face (double-sided mixing process)
Step 1: silk-screen solder paste (top), tiling component, backflow welding, gluing (bottom), tiling element, high temperature curing, backside, inserting element, wave soldering
Step 2: silk-printed solder paste (top surface), paste component, reflow soldering, machine plug (top surface), reverse side, glue (bottom surface), patch, high temperature curing, wave soldering
The top surface of the face adopts perforated components, and the bottom surface adopts the assembly of surface mounting components (double-face mixing technology).
Procedure 1: point glue, stick component, high temperature curing, reverse side, insert element, wave soldering
Procedure 2: machine plug – back – glue – patch – high temperature curing – crest welding
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