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Structure and welding curve of reflow soldering in SMT patch processing

711 Published by FASTPCBA 9月 25,2018

welding curve

The structure of reflow welding is as follows:

1,Total power switch: I is connected to the power supply;O disconnect power.

2 ,color display: display the operation information to facilitate the operator to understand the current working status and accurately display the current parameters of the machine.

3,Keyboard: input information to complete control of the machine.

34,color lamp: display machine working status.

Red: the machine is in A]1ARM state. At this time, the machine cannot work and must be troubleshooting.

Yellow :WARNING status or NEW JOB cut.

Green: the machine is in normal condition.

For example: temperature range of a set temperature is 200 ℃ and normal range set at 15 ℃, the scope of alarm set to 40 ℃, the temperature is 185 ~ 215 ℃ when the green light, the temperature at 160 ~ 185 ℃ or bright yellow lights during 215 ~ 240 ℃, the temperature below 160 ℃ or higher than 160 ℃ when the red light.

5,Press the “RESET” button to initialize the furnace.Press the “RESET” button when the machine starts production.

6,e-stop: in case of an emergency, press this button to cut off all power supply, and only the computer continues to work.

7,EHC KEY: used to adjust the width of the track.

8,H00dkey: used to raise and lower H00D of furnace knot.

9 ,track: used for PCB transmission, there are two kinds of chain network and chain, one side of chain network is produced and the opposite side of chain is produced.

10,refueling bottle: automatically add high temperature chain oil device to the hole to slide the track.

welding curve

welding curve

Phase 1: temperature is to be for about 3 ℃ per second rate rise, to limit the tin in the solvent boiling and fly.If the temperature rises too fast, the solvent will boil, causing the metal powder in the tin cyan to spatter everywhere, causing it to form small tin beads after cooling and solidifying, affecting the electrical properties of the product.In addition, some electronic components are sensitive to temperature. If the external temperature of the component rises too fast, the component will burst.

Stage 2: flux active, chemical cleaning is initiated, and both water-soluble and non-washable flux will undergo the same cleaning operation, albeit at slightly different temperatures.At this time, the flux in the solder paste will quickly damage the surface oxides of the welding materials and the surface of the PCB welded plate, making the component welding end fully contact with the PCB welded plate.

Stage 3: as the temperature continues to rise, the solder particles first melt separately and begin the process of liquefaction and surface absorption of the tin.This covers all possible tables up and begins to form tin solder joints.

Stage 4: this stage is the most important. When the individual solder particles are all melted and combined to form liquid tin, the surface tension begins to form the surface of the solder feet.If the gap between the element pin and the PCB pad exceeds 4 mil, it is likely that the surface tension causes the pin and the pad to be separated, that is, the field point is opened.welding curve 

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