PCB Tech - Matters to be considered in patch processing and related knowledge introduction

Matters to be considered in patch processing and related knowledge introduction
Process description of patch processing
PCB technology is usually mainly used for A-side reflow soldering and B-side wave soldering for surface mounting. This process should be used when only SOT or SOIC (28) pins are used in the SMD assembled on the B side of the SMD process.

SMD processing double-sided assembly: component incoming inspection => single-sided silk-screen solder paste for SMT processing (point SMD glue) => B-side silk-screen solder paste for SMD processing PCB(point SMD glue) => SMD Chip processing => drying => reflow soldering (good only for side B => cleaning => inspection => repair).

Incoming inspection => PCBA-side silkscreen solder paste (dot patch glue) => SMD => Drying (curing) => A-side reflow soldering => Cleaning => Turnover = PCB's B-side dot patch Glue => Patch => Curing => B-side wave soldering => Cleaning => Inspection => Rework)

Double-sided assembly process for patch processing. SMD processing incoming inspection, surface mount screen printing solder paste, need to point SMD glue, SMT processing, drying (curing), A side reflow soldering, cleaning, flipping; surface mount B surface point patch Glue, patch, curing, B-side wave soldering, cleaning, inspection, rework) This process is suitable for reflow on the A-side of the PCB.

SMT chip processing has different package types. Different types of SMT chip processing components have the same shape, but the internal structure and use are very different. For example, TO220 packaged components may be triode, thyristor, field effect transistor, Or double diode. TO-3 packaged components include transistors, integrated circuits, etc. There are also several types of packages for diodes, glass package, plastic package and bolt package. Diode types include Zener diodes, Rectifier diodes, Tunnel diodes, Fast recovery diodes, Microwave diodes, Schottky diodes, etc. All of these diodes use one or more types. Package.

Due to the small components in SMT chip processing, some components do not print. Most commonly used sizes are several, so it is difficult for inexperienced people to distinguish, but SMT chip processing diodes and polarized chip capacitors are easy to distinguish from other patches. Polarized chip components have a common feature, Is the polarity mark.

How to distinguish SMT patch processing? We can distinguish by the type of printing. For devices without characters on the SMT chip processing components, we can also analyze the circuit principle or use a multimeter to measure the component parameters for judgment. Judging the type of SMT chip processing components cannot be learned overnight, it requires years of accumulated experience to understand. It is an electronic assembly technology that originated in the 1980s. It is to mount electronic components, such as resistors, capacitors, transistors, integrated circuits, etc., on a printed circuit board, and form electrical connections through soldering.

The big difference of SMT chip processing plug-in package is that SMT chip processing technology does not need to reserve corresponding through holes for component pins, and the component size of SMT chip processing technology will be much smaller than that of plug-in packaging.