Joy Technology Co.,Limited

General Knowledge of SMT Technology 

1. SMT full name is Surface mount (or mounting) technology, the Chinese means for the surface adhesion (or placement) technology.

2. In general, SMT workshop temperature of 25 ± 3 ℃.

3. Paste
(2) Paste Ingredients include: metal powder, dissolved, flux, anti-flood agent, active agent, the main component of tin powder and flux, the volume ratio of about 1: 1, the weight ratio   
(3) flux in the constant temperature area began to carry out chemical cleaning action. flux in the welding of the main role is to remove the oxide ﹑ destruction of molten tin surface tension to prevent re-oxidation. Rosin-based flux can be divided into four types: R ﹑ RA ﹑ RSA ﹑ RMA.
(4)lead solder Sn / Pb ratio of 63/37, the melting point of 217 ℃. Lead-free solder Sn / Ag / Cu is 96.5 / 3.0 / 0.5, the melting point of 217 ℃.
(5)Paste removed from the refrigerator in Kaifeng use, must go through two important processes back to gentle mixing. The purpose of the temperature is to let the temperature of the cold paste back to room temperature, to facilitate printing. If you do not return to the temperature in the PCB into the reflow after easy to produce tin beads.
(6）Paste access principle is first-in first out.
(7）currently on the market selling solder paste, the actual only 4 hours of sticky time.

4. steel mesh
(1) steel mesh common production methods: etching, laser, electroforming.
(2) Commonly used SMT steel mesh material for the stainless steel. The thickness is 0.15 mm (or 0.12 mm).
(3) SMT general steel mesh openings than the PCB PAD small 4um can prevent the phenomenon of poor solder ball.

5.PCB
(1) often used PCB material FR-4.
(2) PCB vacuum packaging is the purpose of dust and moisture.
(3) PCB warpage specifications do not exceed 0.7% of its diagonal.

6.components
commonly used passive components (Passive Devices) are: resistors, capacitors, inductors, diodes, and so on, and these components are used to pick up the nozzle suction nozzle, referred to as the nozzle or suction nozzle. active components (Active Devices are: transistors, ICs, etc.
components of the control box relative humidity and humidity <10%.
 After the unpacking of the MD, the humidity on the card indicates that the IC is moisture and hygroscopic if it is greater than 30%

7. heating furnace
Reflow furnace temperature curve of the curve of the maximum temperature of 215 ℃ the most appropriate.
tin furnace test, the tin furnace temperature 245 ℃ more appropriate.
RSS curve for the temperature → constant temperature → return → cooling curve. ideal cooling zone curve and the return curve curve mirror relationship.

8. patch red plastic
SMT patch red plastic is a poly-thin compounds, and solder paste is different from its heat after curing, the freezing point temperature of 150 ℃, then, red plastic from the paste directly into a solid body.
SMT patch red plastic with viscosity flow, temperature characteristics, wetting characteristics. According to this feature of red plastic, so in the production, the use of red plastic is to make the parts firmly attached to the PCB surface, to prevent its fall.

For use on presses or dispensers:
① To keep the quality of the patch glue, please store in the refrigerator (5 ± 3 ℃) storage.
② from the refrigerator before use, should be placed at room temperature back to temperature 2 to 3 hours.
③ You can use toluene or ethyl acetate to clean the hose.

Dispensing:
① in the point of the hose to join the plug, you can get a more stable dispensing volume.
② recommended dispensing temperature of 30-35 ℃.
③ When dispensing the hose, please use a special glue sub-machine to separate, to prevent the glue into the glue.

Scraper: Recommended scraping temperature of 30-35 ℃ Note: red plastic removed from the cold environment, before reaching room temperature can not be used.
To avoid contamination of the original product, do not use any of the patch of plastic back into the original packaging.