How to make the soldering fuller when do SMT

In the process of reflow soldering for surface mount technology, the following measures can be taken to make the soldering fuller:

I. Optimize solder paste printing

1. Select appropriate solder paste - Ensure that the alloy composition of the solder paste matches the soldering requirements and has good fluidity and wettability. - According to the size and density of components, select solder paste with an appropriate particle size. Generally, fine-pitch components require solder paste with a smaller particle size.

2. Adjust printing parameters - Control the squeegee pressure, speed, and angle to ensure that the solder paste is evenly printed on the PCB (printed circuit board). - Appropriate increase in squeegee pressure can make the solder paste better fill the stencil openings, but excessive pressure may cause stencil deformation and solder paste overflow. - Adjust the squeegee speed to match the fluidity of the solder paste. Too fast a speed may lead to incomplete solder paste printing, while too slow a speed may affect production efficiency. - Select an appropriate squeegee angle, generally between 45° and 60°, to ensure that the solder paste can be smoothly scraped off the stencil.

3. Check stencil quality - Ensure that the thickness of the stencil is uniform and the opening size is accurate. A too thick stencil may lead to excessive solder paste printing, while a too thin stencil may lead to insufficient solder paste printing. - Regularly check the cleanliness of the stencil to avoid the residual solder paste on the stencil affecting the printing quality.

II. Optimize reflow soldering process

1. Control the reflow soldering temperature profile - Preheating stage: Heat up slowly to make the PCB and components evenly heated and avoid temperature shock. The preheating temperature and time should be adjusted according to the size, thickness, and heat capacity of the PCB. - Soaking stage: Maintain a certain temperature to fully activate the flux in the solder paste and remove oxides on the surface of the PCB and components. The soaking temperature and time should be adjusted according to the characteristics of the solder paste. - Reflow stage: Rapidly heat up to the soldering temperature to melt the solder paste and form a good solder joint with the component leads and PCB pads. The soldering temperature and time should be adjusted according to the alloy composition of the solder paste and the heat resistance of the components. - Cooling stage: Cool down quickly to solidify the solder joint and form a good soldering structure. The cooling speed should be appropriate. Too fast cooling may cause solder joint cracking, while too slow cooling may affect production efficiency.

2. Ensure a good atmosphere in the reflow soldering oven - The oxygen content in the reflow soldering oven should be kept below 100 ppm. Excessive oxygen content may cause solder joint oxidation and affect soldering quality. - Nitrogen protection reflow soldering can be used to reduce solder joint oxidation and improve soldering quality. The purity of nitrogen should be above 99.99%.

3. Check the performance of reflow soldering equipment - Regularly check the heating system, cooling system, and conveyor system of the reflow soldering oven to ensure their normal operation. - Check the temperature sensors and controllers of the reflow soldering oven to ensure accurate temperature control.

III. Optimize the quality of components and PCBs

1. Select reliable components - Ensure that the surface of component leads is clean and free of oxidation and contamination. - Check the lead size and shape of components to ensure they match the PCB pads.

2. Check PCB quality - Ensure that the surface of PCB pads is clean and free of oxidation and contamination. - Check the size and shape of PCB pads to ensure they match the component leads. - Check the uniformity of PCB thickness to avoid affecting soldering quality due to PCB deformation.

IV. Other precautions

1. Keep the production environment clean - Dust and impurities in the production environment may affect soldering quality, so the production environment should be kept clean. - Regularly clean the reflow soldering oven and printing equipment to avoid the influence of residual solder paste and impurities on soldering quality.

2. Train operators - Operators should be familiar with the reflow soldering process and equipment operation methods and operate strictly according to operating procedures. - Train operators' ability to identify and handle soldering defects and discover and solve problems in time.

By comprehensively applying the above measures, the soldering fullness during reflow soldering for surface mount technology can be improved, ensuring the quality and reliability of electronic products.