The main steps of BGA rework process

The main steps of BGA rework process

1, preheating:
PCB and BGA in repair of preheating, constant temperature oven temperature general settings in the 80 to

100 DEG C for 8 to 20 hours, to remove PCB and BGA internal moisture, prevent rework heating generation

blowout phenomenon.

2, remove:
The PCB into the repair station positioning bracket, choose suitable reflow nozzle and set the appropriate

welding temperature curve, start switch, until the end of the program is running, manually remove heat

limelight and vacuum suction pen suck in the BGA.

3, cleaning pad:
PCB and BGA pad clean up, with tin absorption line to drag flat. Second, with a hot iron directly drag flat;

best BGA removed in a relatively short period of time to remove solder, then PBA has not completely

cooled, temperature welding disc injury was less; in the process of removal of solder flux, improve the

activity of soldering tin, to solder removing. In order to assure the BGA Solder joint reliability, the cleaning

pad residual solder paste as far as possible the use of some highly volatile solvent, plate washer water,

industrial alcohol.

4, BGA beads:
In the BGA pad brush evenly coated with solder paste help, select the corresponding planting in Zhujiang

steel net, with the planting of bead stage to grow BGA Solder ball on the corresponding to the BGA pad.

5, BGA solder welding:
In the solder welding table or at the bottom of the heating zone reworkstation on heating, the solder

welding on the bonding pad of the BGA.

6, coating solder paste:
On the PCB pads with brush coated with a layer of solder paste, such as painted too much will cause a

short circuit, on the contrary, it is easy to empty solder, so the solder paste is coated must evenly, to

remove the BGA ball of dust and impurities and to enhance welding quality.

7, paste:
The BGA is mounted on the PCB; the manual alignment, screen frame line as an auxiliary para, tin solder

and solder on the disc surface can by touch to confirm BGA whether to mount, and the reflow melting

when the tension between solder joints have good effect on.

8, welding: will be posted installed BGA PCB is placed in the positioning bracket, hot-air head downward

to the working position, choose suitable reflow nozzle and set the appropriate welding temperature curve,

starting the heating point moving switch operation of welding procedures, until the end of the program

is running, this time square cooling fan began to cool the BGA. Meanwhile, the above hot head lifting,

the hot air and the bottom of the nozzle distance on the BGA surface 8 ~ 10 mm, and keep cool for 30

to 40 seconds, or to be start switch lamp, remove the hot head, then the PCB from the lower heating

zone positioning frame smooth removed.

9, Empty solder: due to manual alignment will make the chip and welding disc produce deviation. The

effect of surface tension of solder ball will make BGA chip and welding disc between the automatic

calibration process. Because of uneven heating, leading to the chip is not uniformly down, or too

early to return to the side of the back side or a corner of the. If at this time to stop reflow, the chip

will not normally fall has coplanarity lead to empty false welding welding phenomenon, so we need

to extend the temperature range of temperature and time, or increase the preheating temperature

of the bottom, so that the melting of the ball was uniformly decreased.

10, Short circuit: when the ball reaches melting point is in a liquid state, if too long or too high

temperature and pressure will caused solder balls on the surface tension and supporting role is

disrupted, resulting in reflow soldering chip falls completely in the PCB plate and short-circuit

phenomenon, so I need to appropriately reduce the a temperature welding temperature and time,

or lowering the bottom of preheating temperature.