How to set up a complete SMT produciton line?

SMT complete line solutions.

Since SMT technology is a complex system engineering involving a number of technologies, strong technology and large investment, how to select and build lines for SMT production equipment with many models is still a complex and difficult work.

The general SMT production process includes three steps of solder paste printing, placement and reflow soldering, and the main equipment is printing machine, placement machine and reflow soldering furnace to form a production line.

Typical SMT scheme:
Loading machine + solder paste printing machine + high-speed placement machine + high-precision placement machine + reflow soldering

Introduction of SMT process equipment
1. Template: (steel mesh) First determine whether to process the template according to the designed PCB. If the chip components on the PCB are only resistors and capacitors and the package is more than 1206, the solder paste can be applied with a syringe or automatic dispensing equipment without making a template; When the chip containing SOT, SOP, PQFP, PLCC and BGA packages in the PCB, as well as the packaging of resistors and capacitors is below 0805, a template must be made. Generally, the template is divided into chemically etched copper template (low price, suitable for small batches, tests and chip pin spacing > 0.635mm); Laser etching stainless steel template (high precision, high price, suitable for high-volume, automatic production line and chip pin spacing <0.5mm). For R&D, small batch production or pitch > 0.5mm, our company recommends etching stainless steel template; For mass production or pitch < 0.5mm stainless steel template with laser cut. The overall size is 370*470 (unit: mm), and the effective area is 300*400 (unit: mm).
2. Screen printing: (Zhichi high-precision semi-automatic solder paste printing machine) Its function is to use a scraper to print the solder paste or patch glue onto the pad of the PCB to prepare for the placement of components. The equipment used is a manual screen printing table (screen printing machine), stencil and scraper (metal or rubber), located at the front end of the SMT line. Our company recommends the use of medium screen printing table, precision semi-automatic screen printing machine method to fix the template on the screen printing table, through the upper and lower and left and right knobs on the manual screen printing table to determine the position of the PCB on the screen printing platform, and fix this position; Then place the PCB to be coated between the screen printing platform and the template, place the solder paste on the screen board (at room temperature), keep the template and PCB parallel, and evenly apply the solder paste on the PCB with a spatula. During use, pay attention to the timely cleaning of the template with alcohol to prevent the solder paste from blocking the leakage of the template.

3. Mounting: (JUKI placement machine, Panasonic placement machine, Siemens placement machine) Its function is to accurately install surface mount components to the fixed position of the PCB. The equipment used is an placement machine (automatic, semi-automatic or manual), vacuum pen or tweezers, located behind the silk screen printing table in the SMT line. For laboratories or small batches, our company generally recommends the use of double-tip anti-static vacuum pen. In order to solve the problem of mounting and alignment of high-precision chips (chip pin spacing <0.5mm), our company recommends the use of South Korea's Samsung automatic multi-function high-precision placement machine (model SM421 can improve efficiency and placement accuracy). The vacuum suction pen can directly pick up resistors, capacitors and chips from the component shelf, and because the solder paste has a certain viscosity, the resistors and capacitors can be directly placed in the desired position; For the chip, a suction cup can be added to the vacuum pen tip, and the amount of suction power can be adjusted by a knob. Remember that no matter what component is placed, pay attention to the alignment position, if the position is misaligned, the PCB must be cleaned with alcohol, re-screened, and repositioned the component.
4. Reflow soldering: (Heller reflow soldering, Flex reflow soldering) Its function is to melt the solder paste, so that the surface mount components and PCB are firmly brazing together to achieve the electrical performance required by the design and are precisely controlled in accordance with the standard curve, which can effectively prevent thermal damage and deformation of PCB and components. The equipment used is a reflow oven (fully automatic infrared/hot air reflow oven), located behind the placement machine in the SMT production line.
5. Cleaning: Its function is to remove the substances that affect the electrical properties or welding residues such as flux on the mounted PCB, and generally do not need to be cleaned if no-clean solder is used. For products requiring micro-power consumption or products with good high-frequency characteristics, cleaning should be carried out, and general products can be cleaned. The equipment used is ultrasonic cleaning machine or direct manual cleaning with alcohol, and the position can be unfixed.
6. Inspection: Its function is to inspect the welding quality and assembly quality of the mounted PCB. The equipment used includes magnifying glass, microscope, and the position can be configured in the appropriate place of the production line according to the needs of inspection.
7. Rework: Its function is to rework the failed PCB, such as solder balls, tin bridges, open circuits and other defects. The tools used are smart soldering irons, rework workstations, etc. Configured anywhere in the production line.
SMT complete line equipment solutions