BGA IC Soldering Technology

Solder Payment Judging Criteria

Top of Interest: Void

Void has no significant impact on reliability. On the other hand, improvement of parameters in the process is necessary. 발생원인
Not enough time for the flux to escape
Pollutants on the circuit board
In an X-ray image,
Appears different from the actual size
The exact dimensions are based on the reference sample.obtained by comparative measurement
Find the cause rather than the exact measurements.It is economical to eliminate factors.

Source of void

solber ball
(air, pollutants, etc.)
(Flux, ball & PCB
usually occurring between faces)
board design
(Via in pad- To Air Expansion)

Void Detected Locations

Mainly between the middle and the top, from the bottom to the top and caught due to lack of time (temperature PROFILE important)
Collapsible ball - 210 ~ 230 ℃
noncollapsible ball - 302℃(90% Pb, 10 Sn) - The frequency of occurrence is also low.

Void Effect

mechanical strength degradation
degradation of heat transfer rate
current resistance increment
Management from large to medium-sized voids reports a slight increase in reliability

X-ray examination

lThe laminography method is expensive, but it is easy to locate voids.
The transmission method is to locate using the tilting function.

Precautions for X-ray Inspection Instrumentation

Voltage Blooming(Phosphor Blooming)
Countermeasures, use of anti-blooming film
comparison measurement with reference sample

Removal of void

Usually, the ball in the BGA IC has few voids.
Optimizing the time-temperature profile of reflow
Flux amount,type,optimize properties

void img void outline

Void Bidding Criteria

ball size, pitch > smaller ; continuous increase in defect

Void Bidding Criteria
Location of Void Class Ⅰ Class Ⅱ Class Ⅲ
Void in ball (dimple)%Dia. / % area 60% of dia=36% of area 45% of dia=20 1/4% of area 30% of dia=9% of area
50% of dia=25% of area 35% of dia=12 1/4% of area 20% of dia=4% of area
[Chart] Voids in Ball at Interface

Solder bridge

reflow condition error
solder spattering
bridging solder ball
Excessive error


BGA IC ball
self-cold lead
Open because the middle ball is smaller than the surrounding ball
Normally, ball diameter is observed to be smaller than quality

Cold solder

Reflow profile bad
Land and ball contact is unstable
weak mechanical adhesion, deterioration of electrical properties, intermittent poor operation, low heat
Cold solder, excess heat
solder splattering
bridge, solder balls

bad and process improvement

Defect bad information
Used to improve yield and quality, usually through visual inspection.
Have a clue to resolve the process defect
Qualitative analysis
First, the stand-off of the square edge should be appropriate, and the shape and size of the ball should be uniform.
Quantitative analysis required
The stand-off uses a laser or touch-probe sensor.
ball diameter
After reflow, for inspection of the pad side of the expansion standard BGA, give an angle and rotate it.
Quantitative measurement S/W is not necessary but useful.
Process trend can be inferred from the trend of quantitative measurement values.

Insufficient/Nneven Heating

When repaired, an ice-heating plate on the back of the BGA of multi-layer PCB and double-sided PCB (defective design)
Cause Insufficient/Uneven Heating, Misalignment

Component Defect

Incorrect parts handling
popcorning(Moisture), warpage(Bending)