The introduction of SMT manual placement process
First, the requirements of manual placement
The installation process is aimed at producing high quality products safely and efficiently, and should meet the following requirements:
Improve production efficiency as much as possible, and achieve the goal by rationally arranging the process and adopting the best operation method under certain human and material resources.
2. Ensure the quality and stability of the product. This point is reflected in the fact that the parts and semi-finished products in the production process have high straight-through rate on the production line, the inspection pass rate of the finished product is high, and the technical indicators are consistent; the failure of the defective products in the finished product has no unstable factors or abnormal faults. appear.
3. Ensure that each component can work properly in the machine with its original performance after installation. The performance of components cannot be reduced or parameter parameters can be changed due to unqualified installation procedures. For example, the installation caused mechanical damage to the components, scratched the outer casing of the machine, and so on.
4. Develop detailed operating practices. For those installation processes that directly affect the performance of the whole machine, special tools are used as much as possible to reduce the randomness of manual operation.
5. The arrangement of the process should be easy to operate, and it is convenient to maintain the orderly arrangement and transmission between the workpieces. During the installation process, large components, auxiliary components, and assemblies should be installed on the rack or the bottom plate. There must be regularity inside and outside, up and down, and left and right during installation. Also pay attention to the shape symbols and markings of each installed device. Position, easy to observe when checking and also pay attention to the order of the combination.
Second, the application range of manual placement
As individual components are loose parts, special components do not have corresponding feeders, or due to various reasons such as pin deformation of the device, it cannot be mounted on the placement machine, as a supplementary sticker after the machine is mounted. Load
2. When producing small or small batches of new product development and development stages;
3. Due to the shortage of funds, no placement machines have been introduced, and the assembly density and difficulty of the products are not very large.
Third, the manual placement process
(1) Applying solder paste
Manual printing paste solder paste process or manual dispensing machine drop solder paste process
(two), manual placement
1. Manual placement tool
(1) Stainless steel scorpion
(2) suction pen
(3) 3-5 times desktop magnifying glass or 5-20 times stereo microscope (for pin spacing below 0.5mm)
(4) Anti-static workbench
(5) Anti-static wrist strap
2, the order of placement
(1) Stick small components first, then stick large components.
(2) Stick the short components first and then the high components.
(3) Light and heavy first. During the installation process, the light components are installed first, followed by the heavy components.
(4) Pre-installation. During the installation process, when the process of splicing, screwing, welding, etc. is used at the same time, it should be connected first, then screwed, and finally welded.
(5) First and then outside. When the assembly is connected to the whole machine, it is first installed from the combination in the rack and then gradually installed outward.
(6) The flow placement station is generally arranged according to the type of component. Each person has one or several components attached; a large number of components can also arrange several placement stations.
(7) An inspection station can be set behind each placement station, or one inspection station can be set behind several stations, or the whole board inspection can be completed after placement. Set according to the density of the assembled board.
(8) Fragile after loading. First install conventional and common components, and then install easy-to-install and fragile components to prevent damage during installation.
(9) Keep the work site clean and orderly, and effectively control the damage caused by the remaining materials.
(10) Installers must be responsible and develop good work habits.
(11) Strict operating procedures, complete protection measures, perfect fire safety and safety rules and regulations are factors that cannot be ignored in production.
3. Manual placement method
(1) Rectangular and cylindrical Chip component mounting method
Hold the component with the tweezers, align the soldering end of the component to the soldering pad at both ends, and place it on the solder paste on the pad. The direction of the component with polarity should be in accordance with the drawing requirements. After confirming the accuracy, gently press it with the tweezers. The solder tail of the component is immersed in the solder paste.
(2) SOT mounting method
Hold the SOT component body with tweezers, align the direction, align the soldering end, and place it on the solder paste on the pad. After confirming the accuracy, gently pry the component body with the tweezers so that the component leads are not less than 1/2 thickness immersed in the solder. In the paste, the component leads are all located on the pad.
(3) SOP, QFP placement method
The 1st or front mark of the device is aligned with the front end mark of the printed board. Use a tweezers or a suction pen to clamp or pick up the device, align the mark, align the two sides or four sides of the pad, center it, and gently press the device body with tweezers. The top surface is such that the component pins are immersed in the solder paste at a thickness of not less than 1/2, and the component leads are all located on the pads. Narrow-pitch devices with pin pitches below 0.65mm should be mounted under a 3-20x microscope.