Ball Grid Array (BGA)

Ball Grid Array (BGA) is a surface-mount package that utilizes an array of metal spheres or balls providing external electrical interconnection. The balls are composed of solder, and are attached to a laminated substrate at the bottom side of the package. The die of the BGA is connected to the substrate either by wire bonding or flip chip connection. The substrate of a BGA has internal conductive traces that connect the die-to-substrate bonds to the substrate-to-ball array bonds.

PBGA

The wire-bonded PBGA (Plastic Ball Grid Array) package is an excellent package for mid- to high-performance devices that require low inductance, ease of surface mounting, relatively low cost, and excellent package reliability. Additional copper layers in the substrate allow for increased power dissipation capability with the Thermally Enhanced PBGA (TEPBGA).

Features:

• Custom substrate designs / ball maps for maximum routing flexibility and electrical performance Custom ball patterns / full arrays / depopulated arrays available Substrates use standard organic PCB manufacturing technology Two or four layer substrates available (ground / power planes) Proven reliability in automotive / industrial environments Capability to withstand lead-free reflow processes (260°C reflow)
• Lead-free solder balls available (95.5% Sn, 4% Ag, 0.5% Cu

TBGA

The TBGA (Tape Ball Grid Array) is a mid to high end BGA packaging solution for applications needing excellent thermal performance without an external heatsink.

Features:

• Improved thermal performance over std PBGA packages <15°c/watt style="font-size: 10pt;">Custom substrate designs / ball maps for maximum flexibility and electrical performance Custom ball patterns / full array / depopulated arrays available; 1.0 mm to 1.27 mm pitch Substrates use standard PCB manufacturing technology Maximum thickness from 1.30 mm to 1.60 mm

• Fine Lines/Spacing Geometry (35/35 μm) on two sides of polyimide substrate

  
  

Ball Shear

The ball shear test is another test to measure the wire bond strength at the first bond through the horizontal shear force. A bond shear tester is required in performing the test which consists of:

1) A shearing arm with a chisel-shaped tool at the end
2) An instrument for measuring the shear strength of the bond

The procedure consists of positioning the shearing tool just beside the ball bond to be tested and slightly above the surface of the first bond pad, then move the tool horizontally against the ball, in effect pushing the ball off its bond pad. The bond shear force is then measured by the ball shear tester in gram-force. The failure modes for ball shear test are as shown below:

1) Ball lifting
2) Ball shear
3) Pad lifting

Figures below show the illustration for ball shear testing and the result of ball shear.

the shear tool's position

the first bond pad showing normal ball shear

the second bond pad showing ball lift

Wire Peel

Wire peel test is a test for wire bond strength at the second bond. It consists of applying an upward force under the wire at the second bond post, pulling the wire away from the bond post. The same wire pull tester is used in performing the test. The failure mode for wire peel test is almost same with wire pull test as shown below:

1) Ball bond lifting
2) Break at stitch
3) Center wire break
4) Second bond or wedge bond lifting

Figures below show the illustration for wire peel testing and the result of break at stitch and wedge lifted.

tool's position

break at stitch

wedge lift

Wire Pull

Wire Pull Test:

Wire pull test is a test for wire bond strength and quality at the first bond. It consists of applying an upward force under the wire to be test, and effectively pulling the wire away from the die. Wire pull tester is required in performing the test, which consists of two parts:
1) A pull hook which is used for applying the upward pulling force on the wire
2) An instrument for measuring the force at which the wire or bond fails. The force is recorded in gram-force.

The procedure consists of applying the pull hook under a wire at the first bond and it’s positioned at the highest point along the loop of the wire, and pulling the wire away from the die through the vertical pull force perpendicular to the die surface. Besides the bond strength, I had to record the bond failure mode as well. The failure mode refers to one of the following:
1) Ball bond lifting
2) Break at neck
3) Break at stitch or heel break
4) Center wire break
5) Pad lifting

wire pull tool's position

ball lift

pad lift

A Visit to Production Line

The production line in Fresscale is mainly about assembly and packaging.

So the concern of R&D is also about the wafer saw, wire bonding, molding

which is from front end to the back end.

This is the bunny suit that we have to wear in order to get into production line.

Basically this is the process chart from front to back end:

First Step: Wafer Mount

- Process of providing support to the wafer to facilitate processes from “Wafer Saw” to “Die Attach”

- Wafer and wafer frame attached on a film

- Things to be prevented:

Ø Wafer cracking

Ø Bubble trapping on adhesive side of tape

Ø Scratches on active side of wafer

Ø Non uniform tape tension

Step 2: Wafer Saw

- Process that cuts wafer into individual dies

Step 3: UV Cure

- Reduce the stickiness on the adhesive side of the tape

Step 4: Die Attach

- Processing of attaching the die to the die pad of the support structure

- Adhesive die attach is the process used using epoxy as the adhesive agent

Step 5: Curing

- To harden the epoxy to form a stronger bond hold with the die

- Done in an oven

Step 6: Wire Bonding

- Process that provides electrical connection between the silicone chip and external leads using bonding wires

- Wires are usually made of Gold (Au)

Step 7: Molding

- Is a process of encapsulating the device in a polymer material

Step 8: Post Curing

- The molded material is then sent for further curing in an oven

- Oven settings:

¡ About 5 hours curing time

¡ 175°C

Step 9: Marking

- Is the process of putting identification, traceability and distinguish marks on IC package (device name, company logo, date code, lot ID)

- Molded compounds are laser marked

Step 10: Cutting

- Leadframe goes through a series of shearing and displacement tools which acts to cut and separate the individual IC units

- LGA units are conventionally sawed to isolate the individual units

- Units are then punched out or picked and placed into their respective container slots

Step 11: Packing

- Lots are bubble wrapped and strapped together

- Depending on types of units/customer request, some units are dry vacuum packed

- Packed units are put into a shipment box

Step 12: Shipment

- Ready lots are shipped out to customers or other departments for further testing

Ouchhhhh!!!!

Dage machine is another machine that I have to deal with.
Somehow it's quite hard to pull out the cartridges.
There are few cartridges that being used here...
such as WP 25, BS25, BS250 and etc..
Today I was trying to change the hook of the wire pull cartridge
as the hook is bent and having difficulties in pulling gold wire..
Unfortunately, my hand was cut by the hook.
Luckily, it was the bent hook that ready to dispose..


Dage Machine


Ouchh...it's bleeeding..:(


Oh!! painfull!!

New Name Tag

Finally get my Name tag!!


well..the name tag of trainee is different with engineers and permanent staffs there.
normally the operator which is in contract also using the same tag.
And there is some kind of 'discrimination' by those operator when seeing this tag
and I don't really like to show the side of my tag.

The VEry 1st task!!

Basically, I am in the wire bonding team under TSO. (Technology Solution Organization) Thus, my tasks are related to measurement and testing on the integrated circuits that have been bond by my supervisor. And basically this is the magnified look of a wire bonded chip.

Under wire bond team..there's few groups of IC such as flip chip, sensor, QFP, RF, BGA and etc. And I am in charge of BGA(Ball Grid Array).

the picture of BGA chip
So the first task that i gonna do is to measure the BBD and BBH by using HISOMET II.

this is the Hisomet II that commonly used in industry
Hisomet is a non-contact depth measuring microscope that has been designed based on the optical focal point detection system.
The precise focus indicator is adopted, so that the measurements of height, depth, steps, etc. are made possible simply by coinciding the two halves of an index graticule while observing the surface of a point of measurement.
As measurements can be made without concern for causing distortion or nicks to a specimen, Hisomet is ideal for measuring electronic components such as ICs and other precision parts.

Hisomet is highly appreciated by manufacturers for its accurate measurements and inspections of objects, such as ICs, magnetic heads, electronic components, precision parts, etc.

Material and forms of specimens used in these industries are diversified.

Precise Focus Indicator

	Focused Condition	Out of Focus Condition
Black graticle
White-stripe graticle

The concern of my team is usually the accuracy of the size of ball bond that produced by wire bonder. BBD (Ball Bond Diameter) is the width of the ball that bond to the die. BBH (Ball Bond Height) is the height of ball that bond to the die.

the digital screen that showing the measurement's values
The X and Y is the values of ball bond diameter
while Z is the height of the ball bond.
In order to get the BBD, we take the mean of measured values of X and Y.

The Hisomet II in the material lab

doing the measurement

observe under scope