DMT243/3
Electronic Packaging
UNIVERSITI MALAYSIA PERLIS
LABORATORY MANUAL
DMT 243/3
ELECTRONIC PACKAGING
LECTURER:
MOHAMMAD NUZAIHAN MD NOR
1
DMT243/3
Electronic Packaging
UNIVERSITI MALAYSIA PERLIS
LABORATORY MANUAL
DMT 243/3
ELECTRONIC PACKAGING
PREPARED BY:
MOHD KHAIRUDDIN MD ARSHAD
MOHAMMAD NUZAIHAN MD NOOR
NURHAMIDAH ABDUL HALIM
MOHD SALLEHUDIN SAAD
Supervised By
Checked By
Approved By
2
DMT243/3
Electronic Packaging
EXPERIMENT 3: WIREBONDING
1.0
Objectives
The objectives of this experiment are:
1. To expose students to wirebonding process and technique.
2. To examine the wirebonding sample under the optical microscope.
2.0
Introduction
Wirebonding is an electrical interconnection technique using thin wire
and a combination of heat, pressure and/or ultrasonic energy. Wirebonding is a
solid phase welding process, where the two metallic materials (wire and pad
surface) are brought into intimate contact. Once the surfaces are in intimate
contact, electron sharing or interdiffusion of atoms takes place, resulting in the
formation of wirebond. In wirebonding process, bonding force can lead to
material deformation, breaking up contamination layer and smoothing out
surface asperity, which can be enhanced by the application of ultrasonic
energy. Heat can accelerate Interatomic diffusion, thus the bond formation.
Wirebonding process begins by firmly attaching the backside of a chip
to a chip carrier using either an organic conductive adhesive or a solder (Die
Attach). The wires then are welded using a special bonding tool (capillary or
wedge). Depending on bonding agent (heat and ultrasonic energy), the
bonding process can be defined to three major processes: thermocompression
bonding (T/C), ultrasonic bonding (U/S), and thermosonic bonding (T/S), as
shown in Table 1.
Wirebonding
Pressure
Temperature
Thermocompression
High
300-500 oC
Ultrasonic
Low
Thermosonic
Low
Ultrasonic energy
Wire
Pad
No
Au,
Al, Au
25 oC
Yes
Au, Al
Al, Au
100-150 oC
Yes
Au
Al, Au
Table 1: Three wirebonding processes.
3.0
Apparatus
1. K&S Model 4524AD
(Wirebonder).
2. Gold wire
3. Capillaries
4. Tweezers
4.0
Multi
Process
Auto
Stepback
Ball
Bonder
Sample
1. Bond Pad Tester
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DMT243/3
5.0
Electronic Packaging
Procedures
Loading the wire and setting the bonding parameters:
Recommended Machine Adjustments
Parameter
Wire clamp gap (μm)
Wire clamp force (gm)
Drag clamp gap (μm)
Drag clamp force (gm)
N.E.F.O. Wand distance from capillary at
Reset (μm)
N.E.F.O. ball size
Tail
Initial Bond Parameter Settings
1st POWER
1st TIME
1st FORCE
1st FORCE (gm)
Setting (gold wire size : 25 μm )
80
100
250
6
500
1.5 – 2.5
4–5
LOOP
1–2
5
1–2
40
4
Second Bond Parameter Settings
Second POWER
Second TIME
Second FORCE
2nd FORCE (gm)
STEP
REVERSE
KINK
Y SPEED
2–3
5–7
4–6
80
2–3
3
2
2
Creating a Ball (manually)
To create a ball:
1.0
Power on the N.E.F.O. unit and set the BALL parameter to the
recommended setting.
2.0
Press the CLAMP control button to open the wire clamp. The green
LED lights.
3.0
Pull some wire from the capillary tip and bend the wire upwards.
4.0
Press the CLAMP control button again to close the wire clamp. The
LED turns off.
5.0
Push and hold the N.E.F.O. solenoid, moving the wand to a position
under the wire.
6.0
Press the MANUAL SPARK control button.
7.0
Verify that a spark was generated and a ball created (in case a ball was
not created, repeat steps 1-6).
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DMT243/3
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Operation
Standard Mode Ball Bonding
The 4524AD performs standard mode ball bonding using Manual Z, Semi Auto
or automatic operation.
To perform Standard Mode Semi Auto ball bonding:
1.0
2.0
3.0
4.0
5.0
Ensure that the bonding head is in the Reset position and that the Mode
is set to STANDARD.
Position the workholder so that the bonding pad is under the capillary.
Ensure that the ball is ready and that the drag and wire clamps are
closed.
Press and hold the Semi Auto Pushbutton. The wire clamp opens and
the kicker pulls out wire slack from the wire spool. The bonding head
descends to the first Search height and stops. The drag clamp pulls the
wire so that the ball is seated against the capillary tip.
While still holding the Semi Auto Pushbutton, move the Multi Mouse to
position the first bonding pad precisely under the capillary.
Release the Semi Auto Pushbutton. The bonding head descends to the
first bonding pad. The first bonding force and ultrasonic energy (set by
the FORCE and POWER parameters) are applied for the time set by
the TIME parameter. The first bond is performed, the drag clamp opens
and the kicker is released.
The bonding head rises automatically to the Kink height position and
travels in a reverse motion to form the Loop shape. The bonding head
then automatically performs Loop height and the table steps forward to
the second bond position.
6.0
7.0
While still pressing the Semi Auto Pushbutton, move the Multi Mouse to
position the second bonding pad precisely under the capillary.
Release the Semi Auto Pushbutton. The bonding head descends to the
second bond pad. The second bond force and ultrasonic energy (set by
the second bond schedule FORCE and POWER parameters
respectively) are applied for the time set by the second bond schedule
TIME parameter.
The bonding head rises automatically to the Reset position. The wire
clamp closes, after which the wire is snapped and creating a tail for a
new ball. The bonding head remains in the Reset position. The
N.E.F.O. wand approaches the tail and fires. A new ball is created for
the next bonding cycle.
To perform Standard Mode Manual Z ball bonding:
1.0
2.0
3.0
Press the MANUAL key on the Keypad.
Use the Manual Z Control Button of the Multi Mouse to lower the
bonding head as close as you want to the bonding pad. Move the Multi
Mouse to maneuver the first bonding pad precisely under the capillary.
Continue pressing the Manual Z Control Button to drop the bonding
head to the bonding pad and perform the bond as in the Semi Auto
mode.
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DMT243/3
4.0
5.0
6.0
7.0
Electronic Packaging
Release the Manual Z Control Button slowly to raise the bonding head
to the Loop height.
Move the Multi Mouse to position the second bonding pad directly under
the capillary.
To perform the second bond, repeat steps 2 and 3.
The bonding head rises to the Reset position automatically. The
N.E.F.O. then fires to create a ball for the next bonding cycle. Release
the Manual Z Control Button to start the next cycle.
To perform Standard Mode Automatic Ball Bonding:
1.0
2.0
3.0
4.0
5.0
Ensure that the bonding head is in the Reset position, that the green
LED next to the MANUAL control button is Off and that the Auto setting
in the Modes Screen is set to On.
Position the workholder so that the bonding pad is under the capillary.
Press and hold the Semi Auto Pushbutton. The wire clamp opens and
the kicker pulls out wire slack from the wire spool. The bonding head
descends to the first Search height and stops. The drag clamp pulls the
wire so that the ball is seated against the capillary tip.
While still holding the Semi Auto Pushbutton, move the Multi Mouse to
position the first bonding pad precisely under the capillary.
Release the Semi Auto Pushbutton on the Multi Mouse. The bonding
head performs the first bond, the loop and the second bond, then rises
to the Reset height and returns to the position of the first bond.
Note: If any additional two-wire bonds are defined, instead of returning
to the first bond position, the bonding head goes to the Reset height.
From there it must be moved manually using the Multi Mouse to the
next bond position.
6.0
Discussion questions
a)
b)
c)
d)
e)
f)
What is actually being tested using the wirebonding machine?
What is an advantage of using Ball/Wedge technique over Wedge/Wedge
technique in the wirebonding process?
Explain about thermocompression, thermosonic and ultrasonic bonding
process.
What is the different between ALL 3 technique automatic, semi-automatic
and manual z in wirebonding process?
Take photos/sketch the location of wirebonding process using ALL 3
technique :
i. Automatic
ii. Semi-automatic
iii. Manual Z
What are the factors that can be affected a wirebonding process?
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