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BGA rework operation process
BGA rework operation process
BGA rework station repair work is completed, operational procedures and precautions are summarized
as follows: the majority of the heat resistance temperature of the semiconductor device is 240 ℃ ~ 600 ℃,
the BGA rework systems, heating and temperature uniformity control is very important.
BGA rework process steps reference:
1. The circuit board, BGA board preheating, the main purpose of the chip is preheated to remove moisture,
if moisture within the circuit board and the BGA is small (eg chip just opened), this step can be dispensed
2. Remove BGA BGA removed if you do not intend to re-use and PCB can withstand high temperatures,
high temperatures can be dismantled BGA (shorter heating cycle).
3. Clean flux left after cleaning pad pad mainly to dismantle BGA in PCB surface, clean out the paste must
be used to meet the requirements of the cleaning agent. In order to ensure the reliability of BGA soldering,
generally can not use the residual paste on the pad, you must paste the old removed, unless the newly
formed BGA BGA solder balls. Due to small size BGA, especially CSP (or μBGA), smaller and more difficult
to clean the pad, so the CSP rework, CSP if the surrounding space is very small, we need to use no-clean
4. The coating paste, flux coated solder paste on the PCB rework results have important implications for
the BGA. By selecting consistent with the BGA template can be easily coated with solder paste on the
circuit board. For CSP, there are three kinds of solder paste can be selected: RMA paste, water-soluble
solder paste and clear Free. Use RMA paste, reflux time may be slightly longer, the use of no-clean
solder paste reflow temperature should be chosen lower.
5. The main objective is to make each mount mounting a solder ball BGA pad on the PCB is aligned.
You must use special equipment to pair.
6. Reflow Reflow is the key to the whole repair process.
(A) BGA Rework reflow soldering curve should be the original curve BGA close, hot air reflow curve can
be divided into four intervals: preheating zone, heating zone, reflux and cooling zones, four intervals of
temperature and time parameters can be are set by connecting to your computer, these programs can
be stored and called at any time.
(B) during the reflow process to select the correct district heating temperature and time, and should pay
attention to the speed of warming. Usually at 100 ℃ previous maximum rate of temperature increase
does not exceed 6 ℃ / s, after 100 ℃ maximum heating rate of not more than 3 ℃ / s, in the cooling
zone, the maximum cooling rate of not more than 6 ℃ / s. Because of high heating rate and the cooling
rate are likely to damage the PCB and BGA, such damage is sometimes not observed visually. Different
BGA, different solder paste, should choose a different heating temperature and time. As CBGA reflux
temperature should be higher than PBGA reflux temperature, 90Pb / 10Sn should be more 63Sn / 37Pb
solder paste selection of higher reflow temperatures. No-clean solder paste, its activity is lower than the
non-clean solder paste. So, not too high welding temperature, welding time not too long, to prevent
oxidation of the solder particles.
(C) hot air reflow, the bottom of the PCB also need to be able heating. There are two such heating
purpose: to avoid the single-sided heat from the PCB warping and deformation; solder paste melting
time is shortened. Large-size panels BGA rework, this bottom heating is especially important.
BGA Rework bottom heating device in two ways, one is the hot air heating, one is infrared heating.
Advantages of hot air heating is the uniform heating, the rework process generally recommend
this heating. The disadvantage is that the infrared heating PCB uneven heating.
(D) to choose a good hot air reflow nozzle. Hot air reflow nozzle is a non-contact heating, relying on high-temperature air flow so that all solder joints on BGA solder melts when heated simultaneously. Ensure a stable temperature environment throughout the reflow process, while protecting adjacent device is not damaged by heat convection hot air return.
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