The characteristics of manual patch proofing: high assembly density, small size and light weight of electronic products. The volume and weight of patch components are only about 1/10 of that of traditional plug-in components. Generally, after SMT is adopted, the volume of electronic products is reduced by 40%~60 %, the weight is reduced by 60%~80%.High reliability and strong anti-vibration ability. The defect rate of solder joints is low.Good high frequency characteristics. Reduce electromagnetic and radio frequency interference.It is easy to realize automation and improve production efficiency. Reduce costs by 30%~50%. Save materials, energy, equipment, manpower, time, etc.

◆Why use surface mount technology (manual patch proofing)?

1. Electronic products are pursuing miniaturization. The perforated plug-in components used before can no longer be reduced, and the functions of electronic products are more complete.Manual patch proofingThe integrated circuits (ICs) used have no perforated components, especially large-scale, highly integrated ICs. Surface mount components have to be mass-produced and automated. The factory must produce high-quality products at low cost and high output to meet Customer demand and strengthen market competitiveness.

2. The development of electronic components, the development of integrated circuits (IC), the multiple applications of semiconductor materials,

The revolution of electronic science and technology is imperative and chasing the international trend.

◆Why use surface mount technology (SMT)?

Electronic products are pursuing miniaturization, and the previously used perforated plug-in components can no longer be reduced.

Electronic products have more complete functions. The integrated circuits (ICs) used have no perforated components, especially large-scale, highly integrated ICs, so surface mount components have to be used.

With mass production of products and automation of production, the factory must produce high-quality products with low cost and high output to meet customer needs and strengthen market competitiveness.

The development of electronic components, the development of integrated circuits (IC), and the multiple applications of semiconductor materials.

The revolution of electronic science and technology is imperative and chasing the international trend.

◆Why is the no-clean process applied in surface mount technology?

1. The waste water discharged after product cleaning during the production process brings pollution to water quality, the earth, and even animals and plants.

2. In addition to water cleaning, organic solvents containing chlorofluorohydrogen (CFC& HCFC) are used for cleaning, which also pollutes and destroys the air and atmosphere.

3. The residue of cleaning agent on the machine board will cause corrosion, which will seriously affect the quality of the product.

4. Reduce cleaning process operation and machine maintenance costs.

5. No-cleaning can reduce the damage caused by PCBA during moving and cleaning. There are still some components that cannot be cleaned.

6. The flux residue has been controlled and can be used in accordance with the product appearance requirements to avoid the problem of visual inspection of the cleaning status.

7. The residual flux has been continuously improved its electrical performance to avoid leakage of the finished product and cause any damage.

8. The no-clean process has passed many international safety tests, proving that the chemical substances in the flux are stable and non-corrosive.

◆Analysis of reflow soldering defects:

Solder Balls: Reasons:

1. The screen-printed hole is not aligned with the pad, and the printing is not accurate, which makes the solder paste dirty the PCB.

2. The solder paste is exposed to too much in an oxidizing environment and too much water in the air.

3. Inaccurate heating, too slow and uneven.

4. The heating rate is too fast and the preheating interval is too long.

5. The solder paste dries too fast.

6. Insufficient flux activity.

7. Too many tin powders with small particles.

8. The flux volatility is inappropriate during the reflow process. The process approval standard for solder balls is: when the distance between the pads or printed wires is 0.13mm, the diameter of the solder balls cannot exceed 0.13mm, or there can be no more than five solder balls within a 600mm square range.

Bridging: Generally speaking, the factor that causes the solder bridge is that the solder paste is too thin. The paste particles are too large and the surface tension of the flux is too small. Too much solder paste on the pad, too high peak reflow temperature, etc.

Open: Reason:

1. The amount of solder paste is not enough.

2. The coplanarity of component pins is not enough.

3. The tin is not wet enough (not enough to melt, and the fluidity is not good), and the tin paste is too thin to cause tin loss.

4. The pin sucks tin (like rush grass) or there is a connection hole nearby. The coplanarity of the pins is particularly important for fine-pitch and ultra-dense-pitch pin components. One solution is to apply tin on the pads in advance. The pin sucking can be prevented by slowing down the heating speed and heating the bottom surface more and less heating on the top surface. It is also possible to use a flux with a slower wetting speed and a high active temperature or a solder paste with different ratios of Sn/Pb to retard the melting to reduce the pin sucking tin.

◆Technical composition related to manual patch proofing

1. Design and manufacturing technology of electronic components and integrated circuits

2. Circuit design technology of electronic products

3. Circuit board manufacturing technology

4. Design and manufacturing technology of automatic placement equipment

5. Circuit assembly manufacturing process technology

6. Development and production technology of auxiliary materials used in assembly manufacturing