What should we pay attention to when applying PCBA three-proof paint?

What does PCBA need to pay attention to when applying three anti - paint?

1. Moisture, dust and salt spray are important factors causing PCBA failure. Electronic circuit board components coated with three anti-salt spray, anti-damp heat, anti-mold paint can resist the impact of harsh environment on circuits and components,

2, increase the mechanical strength and reliability, to prevent the sudden change in temperature caused by condensation between printed wire leakage short circuit or even breakdown,

3, for the printed board working in high voltage and low pressure conditions can improve wire creepage, breakdown phenomenon, so as to improve the reliability of the product.

4. Before PCBA three anti-spraying, the printed board needs to be cleaned. To achieve the cleanliness index, the commonly used cleaning methods include alcohol, gasoline, trichloroethylene or water cleaning process,

5, recommend the use of water cleaning technology, the cleaning process is green and environmental protection, using the process can completely and effectively remove the flux residue.

6. The power module of PCB board components containing power modules is usually poked with silicone oil and soaked in solvents such as alcohol and gasoline, which is easy to produce chemical reactions.

7. The surface is polluted by silicone oil. When PCBA is polluted by silicone, the coating will produce discontinuous areas. Cause the coating can not be uniformly attached to the surface and affect the protection performance,

8. For the printed board with power module devices, the actual work is usually done by dipping solvent for local scrubbing, to avoid the leakage of silicone oil in the power module and pollution of the board.

9, resulting in non-stick paint affect the protection performance. To investigate the protective effect of the coating is actually to investigate the degree of combination between the coating and the solder resistance film.

Different welding resistance film due to composition, content differences, and coating binding force is inconsistent. The adhesion degree of the coating is closely related to the molecular polarity of the solder resistance film and the coating. The surface polarity of the matte solder resistance film is not miscible with the polarity of the three coatings

2. Basic knowledge of red glue process in SMT plant

SMT patch factory core tips: SMT patch red glue process is a kind of poly compound, different from solder paste is that it is cured after heat, its freezing point temperature is 150℃, at this time, red glue begins to paste directly into a solid.

SMT red glue process is a kind of poly compound. Different from solder paste, it is cured after being heated, and its freezing point temperature is 150℃. At this time, red glue begins to change from paste to solid directly.

SMT red glue has viscosity fluidity, temperature characteristics, wetting characteristics, etc.

According to this characteristic of red glue, the purpose of using red glue in production is to make the parts stick firmly on the surface of PCB and prevent them from falling off.

Printing press or dispensing machine use:

1. In order to maintain the quality of the patch adhesive, please store it in the refrigerator (5±3℃);

2, remove from the refrigerator before use, should be placed at room temperature for 2 to 3 hours;

3. Toluene or ethyl acetate can be used to clean the hose;

SMT factory process dispensing:

(1) A more stable dispensing quantity can be obtained by adding the plug in the dispensing hose;

The recommended dispensing temperature is 30-35℃;

(3) When decorating the rubber hose, please use the special glue moisture machine to separate the rubber, so as to prevent the mixing of bubbles in the glue. The recommended scraping temperature is 30-35℃. Note: After the red rubber is removed from the refrigerated environment, it cannot be opened and used before it reaches the room temperature. To avoid contamination of the original product, no used patch glue shall be returned to the original packaging.

1) Printing method: steel mesh holes should be determined according to the type of parts, the performance of the substrate, the thickness and the size and shape of the holes. Its advantages are fast speed and high efficiency.

2) Dispensing method: Dispensing is to use compressed air to point red glue to the substrate through the special dispensing head. The size and amount of the glue point are controlled by time, pressure tube diameter and other parameters. The dispensing machine has flexible functions. For different parts, we can use different dispensing head, set parameters to change, can also change the shape and quantity of the glue point, in order to achieve the effect, the advantages are convenient, flexible, stable. Disadvantages are easy to have wire drawing and bubbles. We can adjust the operating parameters, speed, time, air pressure and temperature to minimize these shortcomings.

3) Needle rotation mode: It is to dip a special needle film into the shallow glue dish and each needle has a glue point. When the glue point contacts the substrate, it will be removed from the needle. The amount of glue can be changed by the shape and diameter of the needle.

Curing temperature 100℃ 120℃150℃ Curing time 5 min 150 s 60 s Typical curing conditions:

Points to note:

1. The higher the curing temperature and the longer the curing time, the stronger the bonding strength.

2, because the temperature of the patch adhesive will change with the size of the substrate parts and the installation position, so we recommend to find out the most suitable hardening conditions. Storage of red glue: it can be stored for 7 days at room temperature, more than 6 months at less than 5℃, and more than 30 days at 5 ~ 25℃.

Because SMT patch red glue is affected by temperature with its own viscosity, fluidity, wetting and other characteristics, so SMT patch red glue must have certain conditions of use and management of patch red glue specifications.

1) Red glue should have a specific flow number, according to the number of feed, date, type.

2) Red glue should be stored in the refrigerator at 2 ~ 8℃ to prevent the characteristics from being affected due to temperature changes.

3) The return temperature of red glue is required to be at room temperature for 4 hours, in the order of first in, first out.

4) For the dispensing operation, the red glue of the rubber hose should be defrosted, and the one-time unused red glue should be put back in the refrigerator for preservation. The old glue and the new glue can not be mixed.

5) To accurately fill in the temperature return record form, temperature return person and temperature return time, users need to confirm the completion of temperature return before use. Generally, red glue cannot be used out of date. We undertake SMT patch processing orders, looking forward to your arrival!