*NeW LiFE*

Ball Shear Test


Review.... ...


-This is a destructive test ( non-reversible process to test the strength of the specimen)

- The purpose of doing this test is to measure the metallurgical adhesion of the ball bond to the die pad

-The equipment used to perform this test are DAGE 4000 with BS500 catridge


BS 500 Cartridge

The procedures for ball shear test:

1. The shear tool has to be placed just beside the ball bond slightly above the surface of the first bond pad

2. The shearing arm then moves the tool horizontally against the ball which eventually pushes the ball off its bond pad.

3. Readings, types of failure modes and pictures of failures are recorded.

Table for Ball Shear Test Failure Modes Optical Images After Ball Shear Test :





Appendix


Optical Image after Ball Shear Test




Failure Mode


Lifted Metal



Lifted Ball

Wire pull And Wire Peel Steps


When I do the wire pull and wire peel test, there might be different failure mode.


Hence, while doing the testing I have to observe the failure mode at the same time and record it.


Some failure Mode may cause by the hook I using was bent, the pull & peel speed, the bonding parameter and etc...



The table for the failure mode is same for both wire pull and wire peel test!!

The step in doing the wire pull test

1. The wire pull hook was placed at the first kink (at the highest point along the loop of the wire), then the bonded wire was pulled away from the die with the hook.
2. The pulling force is usually applied perpendicular to the die surface. The breaking force is measured in gram.
3. Readings, types and pictures of failure mode are recorded

The steps in doing wire peel test

1. The hook is placed as close to the standardized position at the edge of the second bond pad as possible so that the failure will be at the second bond.

2. Normally wire bond at the corner of the chips will be chosen. This is due to the corner wire bonded is longest, hence weakest strength.

3. Readings, types of failure modes and pictures of failures was recorded. The failure modes are same as wire pull failure modes.

The wire at 2^nd bond before wire peel test (top) and after wire peel test (bottom)

The photos below show the failure mode that may cause in the task, the photos in taken by using HISOMET :

From left to right : Lifted Ball. Break at Neck, Lifted Metal

Overall Process

The process flow for the chips from the front end to the back end and ultimately to the customers..

(a) Wafer is Built
This is the process where the wafer is formed by many dies and it is in a round shape)

(b) Wafer Mount
To stick wafer on a tape with ring

(c) Wafer Saw
To cut off the dies individually

(d) Die Bond
To bond the die on the substrate using epoxy

(e) Plasma Cleaning
To clean the substrate with plasma that carried out by Argon(physically) ans Oxygen(Chemically)

(f) Wire Bond
To connect the gold wire from the bond pad of the die to the lead finger on the substrate

(g) Plasma Cleaning Repeated
To clean the bonding part with plasma

(h) Mold
To liquified mold compound fills the cavities around the die

(i) Post Cure
To molded material sent for further curing in an oven

(g) Solder Ball
The balls are soldered on the back of the substrate on the specific location

(h) Reflow Cure
Heat the soldered ball for better cAontact with substrawte

(i) Laser Marking
Mark the components with model number

(j) Singulation
Cut the strips into a single unit of the substrate

(k) Shipping
To ship the product to the customer

(b) Second Bond Placement


Basically,this is the placement of the crescent of the second wire bond with respect to its designated substrate bond post.


The Photos show how the measurement have been done:

1. Place the green line on the left of the pad


2. Move the green line by rotate the X-axis.By doing so, i can get X1 value.


3. To find X2, same procedures have been done as step1&2 on the right side.


Crescent Width, W= PW-(x1+x2)

(c) Loop Height

This test should be repeated for each grouping. For different grouping of wires, there are the specific limit for the wire. If the measurement is not within the limit, it is consider failed.


Cross-section view for different grouping of bonded wires:


Layer1 - Ground

Layer2- Power Ring 1

Layer3- Power Ring 2

Layer4- Inner Bond Post

Layer 5- Outer Bond Post


(d) Ball-Bonded Diameter(BBD) & (e) Ball Bonded Height (BBH)


Normally, this two measurement will be found at the same time.
The purpose for the test is to evaluate the shape and dimensions of the ball formed

BBD:
1. Measure the gold ball diameter(x&y axis) by setting the red cross line at the edge of the ball.
Photo show the red line is putting at the left side and the bottom side of the bonded ball.


2. Then, it is move from left to right and bottom to up.

THE END ~HIsOmET~!

HISOMET is a machine that i used the most in my working life.


This is because HISOMET is used for :

(a) 1st bond placement measurement

(b) 2nd bond placement measurement

(c) Loop height

(d) Ball-bonded Height (BBD)

(e) Ball- bonded Diameter(BBH)


Let's talk about what is 1st bonded placement... ...


The two Cpk's will use actual measurements of the cone size, squashed ball size from the same ball bonds :

(a) Benchmark

The 2 photos show how I measure the cone size value for the left hand side, and same step will be done in right hand side.

The value that I get will use to get the Benchmarking Cpk.




(b) Internal


While this 2 photos show how I measure the squashed size value for the left hand side, and same step will be done in right hand side.

The value that I get will use to get the Internal Cpk.




In order to capture the range of the wire bond placement capability as fully as possible, there are a few considerations i have to take note in selecting which ball bonds to be measure :
1. Different groupings of wires
Select ball bonds created from different groupings of wires

2. Different side of the dice
Ball bonds from all four sides of the dice should be included

3. Location of dice on substrate strip
Select dice that are far apart from each other on the substrate strip to measure the placement variation

4. Strip
Select strips that were wire bonded at different times within an assembly lot. For example, select first strip. middle strip and last strip of a magazine


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