1. Chip Carrier Package as an Alternative for Known Good Die
Raymond Kuang
September 08, 2004

2. Driver for Known Good Die (KGD)
Applications which require integration of different die technologies in one board (Multi-Chip- Package, System-in-Package, etc) and where the cost of board rework due to bad die is severe.
Major markets are portable electronic products.
The advent of small footprint packages like Chip Scale, Wafer Scale, etc offers a low cost alternative for low end applications.
High end systems which require limited weight and space.

3. Limitation of KGD
High end KGD for high end application is difficult to obtain.
Limited to small I/O devices due to technical difficulties.
Full screening through the fine bond pad pitch in today’s sub-micron silicon technology is an issue.
Each die size for KGD normally requires custom socket.
Marking for traceability, such as wafer lot, is not possible.
Mil-Std-883 requires traceability for Space Application devices.

4. Chip Carrier as an Alternative Solution for KGD
17 mm
17 mm
Total Thickness : mm
256 Bond fingers on edges of package

5. Chip Carrier as an Alternative Solution for KGD
Advantages:
Designed for high density I/O where bare die testing is not technically and economically feasible.
Testing and Programming the device through the package terminal is reliable.
Voltage and currents are controlled with the use of low socket
impedance.
Testing and programming are same as package parts like BGA or LGA. They are cost effective and reliable
Can accommodate many die sizes in one Chip Carrier package outline.
No custom socket is needed for each die configuration.
Can be marked for unit traceability (wafer lot#, etc).

6. Chip Carrier as an Alternative Solution for KGD… con’t
Features
Small Foot print.
Can be used for both wire bond and flip chip version.
Wire bond version.
Smallest size is around bare die size mm.
Flip Chip version.
Smallest size is bare die size mm.
Lead finger for wire bond use
Pads for Test/Programming use or BGA connection

7. Chip Carrier as an Alternative Solution for KGD… con’t
Two terminals available for each signal:
External lead fingers on the top sides – for wire bond from package to MCM use.
Land grid pads at the bottom – primarily for test use. Can be utilized for BGA connection to the MCM board also.
Chip Carrier material can be ceramic, organic or other suitable materials.
Multi-layer build-up substrate to enhance electrical performance and routing for high density I/O applications.

8. Method to Integrate into MCM
Wire bond top lead fingers to system board to route out signal.
Chip Carrier must be attached using electrically non-conductive epoxy to system board.
epoxy
Wire bond version
Flip Chip version

9. Method to Integrate into MCM…con’t
Use the land pads at the bottom of the package.
Chip Carrier can be connected using solder balls and reflow to the system board.
Solder ball
Wire bond version
Solder ball
Flip Chip version

10. Manufacturing Issue and solution
Major concern is contamination on external bond fingers that may affect board level wire bonding reliability.
Due to poor handling at assembly and test, and equipment cleanliness.
use of contaminated finger cots in handling the unit, use of contaminated perfluorocarbon bath at gross leak test, out gassing from contaminated burn-in board, etc…
Handling-induced contamination can be prevented by the use of clean vacuum pen to “pick and place” the units.

11. Manufacturing Issue and solution… con’t
A good control to prevent contamination of accessories like trays/boats, sockets, etc. use in the assembly and test of the parts must be in place.
Use of low power microscope at visual inspection is necessary.
Wet cleaning using Isopropyl Alcohol can be used to remove most surface contamination induced during assembly and test screening.
Recommended to do plasma cleaning prior to wire bonding at Multi-Chip-Module or board level assembly.

12. Bond Finger Reliability at Board Level
Chip Carrier units were exposed to different handling conditions, attached and wire bonded to a ceramic package and aged at 150C environment. A bond pull test was done to determine the interconnect reliability.
Ceramic Chip Carrier
Ceramic Land Grid Array Package
Gold bond

13. Reliability Evaluation… con’t
Details

14. Reliability Evaluation… con’t
Notes:
Cleaning process
Wet – used Isopropyl Alcohol, and de-ionized (DI) water.
Plasma – used 100% Argon gas
Bond pull Strength test Sample size:
As-bonded: wires/unit
Post 500 hrs HTS: 100 wires/unit
Wire bond Strength Pull modes
1 – break at neck above the ball
2 – break at wire span
4 – break at wedge bond
CC256
LGA
Chip Carrier
mode 1
Au wire
Bond pull hook
mode 4
mode 2

15. Reliability Evaluation… con’t
The bond strength pull mode were at wire neck above the gold ball, and at wire span.
The absence of gold ball-to-lead finger separation indicates good gold wire bonding to Chip Carrier’s lead finger.
The bond strength measured on samples were above the Mil-Std-883 TM2011 minimum requirement.

16. Summary
Actel’s near-die size Chip Carrier is a viable alternative for Known-good-die (KGD). It eliminate the challenges associated with handling, testing, and programming of today’s high I/O, high density devices in bare die format.
Chip Carrier can be used in both flip chip or wire bonding format.
A slight deposit of contamination coming from the environment and handling during assembly and test is expected on external bond fingers of Chip Carrier. However, this can be controlled by implementing good handling and cleaning procedure.
Thanks!