BGA repairs

BGA repairs

Since the BGA package is different from the conventional surface element, the pin is distributed in the

bottom of the element, so the maintenance mode of BGA is also different from the traditional surface

element.

BGA rework process mainly includes the following steps:
1 circuit board, chip preheating
2 dismantling chip
3 cleaning pad
4 with the solder paste, flux
5 patch
6 hot air reflow

1) circuit boards, chip preheating, the main purpose is to remove the moisture, if the moisture of the

circuit board and the chip is small (such as chip just unpacking). This step may be exempted from.

2) if the chip is not intended to be re used, and the circuit board can withstand high temperature, the

removal of the chip can be used for a higher temperature (shorter heating period). 3) cleaning pad is

mainly the chip removed after remaining on the surface of the PCB soldering flux, solder paste clean

out must be used in accordance with the requirements of cleaning agent. In order to ensure the

reliability of the welding of BGA, the general can not use the solder on the old residual solder paste,

you must remove the old solder paste, unless the chip on the formation of BGA solder ball. Due to

the small size of the BGA chip, especially the smaller size of the CSP chip, it is difficult to clean the

pad. So in the revision of the CSP chip, if the CSP around the space is very small, it requires the use

of non cleaning flux.

4) in PCB coated with solder paste has important effect on BGA repair results. In order to accurately

and evenly coated solder paste, the United States OK group to provide MS-1 micro solder paste

printing plate system. By selecting the template with the chip, it can be easily applied to the circuit

board. When selecting a template, you should note that the BGA chip will be thinner than the thickness

of the CBGA chip, as they are required for different solder paste. OK group of BGA3000 equipment or

MP-2000 micro optical system can be easily tested solder paste is uniform. Processing CSP chip,

there are 3 kinds of solder paste can be selected, RMA solder paste, non - clean solder paste,

solder paste. The use of RMA solder paste, reflux time can be slightly longer; the use of non

clean solder paste, the low temperature should return.

5) the main purpose of the patch is to make each of the solder balls on the BGA chip and the

solder joints on the PCB. Since the solder joints of the BGA chip are located at the site where

the eye can not be observed, special equipment must be used to. BGA3000 and MP-2000

devices manufactured by OK group can perform these tasks accurately.

6) hot air reflow is the key to the repair process. Several problems are important:

Chip rework reflow curve should be and chip of the original welding is similar to the curve and use

the OK group of BGA3000 can ensure do this. Its hot air reflow curve can be divided into four sections:

preheating zone, heating area, recirculation zone, cooling zone. The temperature and time parameters

of the four interval can be set respectively, and the program can be stored and called by the computer.

The heating temperature and time of a district should be selected correctly in the process of

reflow soldering, and the temperature should be paid attention to. The maximum heating rate is not

more than 6 C / s at 100, and the maximum heating rate is no more than 3 for 100, and the maximum

cooling rate is no more than 6. Because of the high temperature and cooling rate of the possible

damage to the PCB and chip, this damage can sometimes be observed by the naked eye.

BGA rework equipment OK group can easily choose to use this computer. Different chips,

different solder paste, should choose different heating temperature and time. Such as CBGA chip

of the return temperature should be higher than the return of PBGA temperature, 90Pb/10Sn

should be more than 73Pb/Sn solder paste selection of higher reflow temperature.

In the hot air reflow soldering, the bottom of the PCB plate must be capable of heating. There are two

purposes of this kind of heating: to avoid the heat caused by the heat of the PCB plate and the

distortion of the time, the time of the Han Xigao melting. For large size plate repair BGA, the bottom

heating is especially important. At the bottom of the heating BGA rework equipment OK group has

two kinds: one is the hot air heating, infrared heating is a. The advantages of hot air heating is uniform

heating, general repair process recommended by this heating. Infrared heating has the advantage of

increasing the temperature, but the disadvantage is that the PCB is not uniform.

To choose a good hot air return nozzle. Hot air return flow nozzle is non contact heating, heating,

the BGA chip on the hot air flow to make the solder on the solder joints at the same time. OK group

first invented this nozzle, it will be BGA component seal, to ensure a stable temperature environment

throughout the return process, while protecting the adjacent components are not heated by convection

heat damage.