XAVIS

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.)

Reflow
(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

01
mechanical strength degradation

02
degradation of heat transfer rate

03
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 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

bridging

Opens

BGA IC ball
self-cold lead

nonwetting

open

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)

INFORMATION

BGA IC Soldering Technology

Solder Payment Judging Criteria