PCBA Tech - SMT patch electrostatic management standards, testing methods

SMT processing is an important step in chip production and processing. After SMT processing, product processing can be further carried out. However, many people do not know the process of SMT processing, and do not know the main points of SMT processing.

1. SMT processing flow

1. Edit the program to adjust the placement machine

According to the sample BOM placement location map provided by the customer, perform the program for the coordinates of the placement component. Then the first piece is matched with the SMT patch processing data provided by the customer.

2. Printing solder paste

The solder paste is printed on the PCB board with the stencil on the pads of the SMD of the electronic components that need to be soldered to prepare for the soldering of the components. The equipment used is a screen printer (printing machine), located at the front end of the SMT patch processing production line.

3. SPI

The solder paste detector detects whether the solder paste printing is a good product, whether there is little tin, leaking tin, excessive tin and other undesirable phenomena.

4. Patch

Install the electronic components SMD accurately on the fixed position of the PCB. The equipment used is a placement machine, located behind the screen printing machine in the SMT production line.

The placement machine is divided into high-speed machine and general-purpose machine

High-speed machine: used to paste large and small components

General-purpose machine: small-pin spacing (pin dense), large-volume components.

5. Melting of high temperature solder paste

The main purpose is to melt the solder paste at high temperature, and after cooling, make the electronic components SMD and PCB board firmly welded together. The equipment used is a reflow oven, which is located behind the placement machine in the SMT production line.

6. AOI

Automatic optical detector, to detect whether the welded components have poor welding, such as tombstone, displacement, empty welding, etc.

7. Visual inspection

The key items for manual inspection: whether the PCBA version is the changed version; whether the customer requires components to use substitute materials or components of designated brands and brands; IC, diodes, transistors, tantalum capacitors, aluminum capacitors, switches, etc. Whether the direction of the directional components is correct; defects after welding: short circuit, open circuit, fake part, fake welding.

8. Packaging

Qualified products will be packaged separately. The generally used packaging materials are anti-static bubble bags, electrostatic cotton, and blister trays. There are two main packaging methods. One is to use anti-static bubble bags or electrostatic cotton into rolls and separate packaging, which is currently a common packaging method; the other is to customize blister trays according to the size of PCBA. Place the package in a blister tray, mainly for PCBA boards that are sensitive to needles and have vulnerable SMD components.

Two, SMT processing points

1. When performing SMT processing, everyone knows that solder paste is needed. For the solder paste just purchased, if it is not used immediately, it must be stored in an environment of 5-10 degrees. In order not to affect the use of the solder paste, it must not be placed in an environment below zero.

2. When the SMT processing technology is in the placement process, the placement machine equipment must be checked frequently. If the equipment is aging, or some components are damaged, in order to ensure that the placement will not be crooked and high throw In the case of materials, the equipment must be repaired or replaced with new equipment. Only in this way can production costs be reduced and production efficiency improved.

3. When performing SMT processing, if you want to ensure the quality of PCB board soldering, you must always pay attention to whether the setting of reflow soldering process parameters is very reasonable. If there is a problem with the parameter setting, the quality of PCB board soldering will not be possible. Guaranteed. Therefore, under normal circumstances, the furnace temperature must be tested twice a day, and the furnace temperature must be tested once every day. Only by continuously improving the temperature curve and setting the temperature curve of the welding product can the quality of the processed product be guaranteed.