U.S. patent application number 10/693078 was filed with the patent office on 2005-04-28 for daisy chain gang testing.
Invention is credited to Grilletto, Carlo.
Application Number | 20050088195 10/693078 |
Document ID | / |
Family ID | 34522287 |
Filed Date | 2005-04-28 |
United States Patent
Application |
20050088195 |
Kind Code |
A1 |
Grilletto, Carlo |
April 28, 2005 |
DAISY CHAIN GANG TESTING
Abstract
A method and system for testing an integrated circuit package is
disclosed. The integrated circuit package includes a plurality of
daisy chain loops that are connected to a pair of package pads,
wherein adjacent daisy chain loops are oppositely biased. Aspects
of the present invention include forming a first plurality of gangs
of electrically coupled daisy chain loops having a first bias and
forming a second plurality of gangs of electrically coupled daisy
chain loops having a second bias. Each one of the first plurality
of gangs is individually coupled to an electrical measurement
device, while the second plurality of gangs are electrically
coupled in common, and the common gang is coupled to the electrical
measurement device. According to the method and system disclosed
herein, the electrical measurement device may be used to indicate
whether there is any leakage between one or more of the first
plurality of gangs and the common gang, thereby eliminating the
need to use an ATE tester and device under test (DUT) circuit board
to perform reliability tests.
Inventors: |
Grilletto, Carlo; (San
Carlos, CA) |
Correspondence
Address: |
LSI LOGIC CORPORATION
1621 BARBER LANE
MS: D-106
MILPITAS
CA
95035
US
|
Family ID: |
34522287 |
Appl. No.: |
10/693078 |
Filed: |
October 23, 2003 |
Current U.S.
Class: |
324/754.02 |
Current CPC
Class: |
G01R 31/2879 20130101;
G01R 31/2886 20130101 |
Class at
Publication: |
324/765 |
International
Class: |
G01R 031/26 |
Claims
1. A method for testing an integrated circuit package having a
plurality of daisy chain loops, each daisy chain connected to a
pair of package pads, wherein adjacent daisy chain loops are
oppositely biased, the method comprising: (a) forming a first
plurality of gangs of electrically coupled daisy chain loops having
a first bias; (b) forming a second plurality of gangs of
electrically coupled daisy chain loops having a second bias; (c)
individually coupling each one of the first plurality of gangs to
an electrical measurement device; (d) electrically coupling the
second plurality of gangs in common, forming a common gang, and
coupling the common gang to the electrical measurement device; and
(e) using the electrical measurement device to indicate whether
there is any leakage between one or more of the first plurality of
gangs and the common gang, thereby eliminating the need to use an
ATE tester and device under test (DUT) circuit board to perform
reliability tests.
2. The method of claim 1 further including the step of:
electrically connecting the first and second pluralities of gangs
in parallel to a first and second edge card connectors.
3. The method of claim 2 further including the step of: coupling
the first and second edge card connectors to a gang testing
board.
4. The method of claim 3 further including the step of: providing
the gang testing board with wire fingers for coupling the first
plurality of gangs to the first edge card connector and for
coupling the second plurality of gangs to the second edge card
connector.
5. The method of claim 4 further including the step of: if the
electrical measuring device indicates a leak is present, then
electrically coupling each one of the second plurality of gangs to
the electrical measurement device, and electrically coupling the
first plurality of gangs in common, and coupling the common gang to
the electrical measurement device; and using the electrical
measuring device to identify which one of the second plurality of
gangs is leaking.
6. The method of claim 5 further including the step of: (h)
manually probing to identify which one of the daisy chained loops
in the identified gang is leaking.
7. The method of claim 6 wherein the first bias is positive and the
second bias is negative.
8. The method of claim 7 wherein adjacent gangs formed by the wire
fingers are oppositely biased.
9. The method of claim 8 wherein the electrical measuring device
comprises a data logger.
10. The method of claim 8 wherein the electrical measuring device
comprises an ohm meter.
11. The method of claim 4 wherein the gang testing board is
provided with edge card connectors on all four sides.
12. A reliability testing system for testing integrated circuit
packages, comprising: a test package mounted to a test socket
wherein the test package includes an array of pads in which pairs
of the pads are connected to form daisy chain loops, wherein
adjacent lines of the daisy chain loops alternate between having a
first bias and a second bias; a gang testing board on which the
test package and the test socket are mounted, the gang testing
board including, a first edge card connector, a second edge card
connector, and wire fingers, wherein the wire fingers are coupled
to the pads of the test package such that multiple gangs of daisy
chain loops having the first bias are coupled to the first edge
card connector, and multiple gangs of daisy chain loops having the
second bias are coupled to the second edge card connector; an
electrical measuring device coupled to the first and second edge
card connectors for measuring cumulative leakage between the
adjacent lines of the daisy chain loops, wherein the first edge
card connector individually couples each one of the gangs having
the first bias to the electrical measuring device, and the second
edge card connector electrically shorts each of the gangs having
the second bias to form a common gang, and the common gang is
coupled to the electrical measuring device; and wherein the
electrical measuring device indicates whether there is any leakage
between one or more of the gangs having a first bias and the common
gang, thereby eliminating the need to use an ATE tester and device
under test (DUT) circuit board to perform reliability tests.
13. The system of claim 12 wherein the gangs are electrically
connected in parallel to the first and second edge card
connectors.
14. The system of claim 13 wherein if the electrical measuring
device indicates a leak is present, then the test is repeated by
(a) electrically coupling each one of the gangs having the second
bias to the electrical measurement device, and electrically
coupling the gangs having the first bias, and coupling the common
gang to the electrical measurement device, and (b) using the
electrical measuring device to identify which one of the second
plurality of gangs is leaking.
15. The system of claim 14 wherein which one of the daisy chained
loops in the identified gang is leaking may be identified through
manual probing.
16. The system of claim 15 wherein the first bias is positive and
the second bias is negative.
17. The system of claim 16 wherein adjacent gangs formed by the
wire fingers are oppositely biased.
18. The system of claim 17 wherein the electrical measuring device
comprises a data logger.
19. The system of claim 17 wherein the electrical measuring device
comprises an ohm meter.
20. The system of claim 12 wherein the gang testing board is
provided with edge card connectors on all four sides.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method and apparatus for
testing integrated circuit packages, and more particularly to a
method and system for performing reliability testing of integrated
circuit packages without using an automatic electrical tester.
BACKGROUND OF THE INVENTION
[0002] Integrated circuits are typically packaged before they are
used with other components as part of a larger electronic system.
Ball grid array (BGA) packages, for example, are constructed with
die mounted on a substrate, and an array of solder balls mounted on
the bottom of the substrate are used to attach the package to a PC
board or motherboard. In contrast, molded plastic packages use lead
frames on the outer edges of the package substrate to attach the
package to the PC board.
[0003] In order to test the reliability of the integrated circuit
packages, the packages are subjected to multiple electrical stress
tests. To perform some types of tests, metallization routing is
used to bridge package substrate traces, creating simple electrical
"loops" between pairs of BGA balls or lead frames. These electrical
loops are commonly referred to as daisy chain loops.
[0004] One procedure performed on the IC package during reliability
stress testing is to oppositely bias parallel connected daisy chain
loops and measure cumulative leakage between the parallel loops.
Although the leakage test is a simple one, almost all stress
testing performed today is done with the use of an expensive
Automatic Electrical Tester (ATE) and an expensive Device Under
Test (DUT) circuit board. The purpose of an ATE is to functionally
test the die in the IC package and is programmable. Therefore, an
ATE is both complicated and expensive.
[0005] Using such a complicated and expensive tester to perform
simple leakage testing and other such test is an inefficient use of
resources that cost semiconductor manufacturers time and money. For
example, a typical ATE may cost between $1 million to $5 million
dollars. In addition, a DUT board may cost between $8,000 and
$12,000 for each IC package design. Thus, it is not uncommon for a
semiconductor manufacture to spend $350,000 a year for DUT boards.
In addition, there is a current time factor of 4 days between the
time the sample is submitted for the ATE test and the results are
obtained.
[0006] Accordingly, what is needed is an improved method and system
for performing leakage testing on IC packages that eliminates the
need to use an expensive and time-consuming ATE tester. The present
invention addresses such a need.
SUMMARY OF THE INVENTION
[0007] The present invention provides a method and system for
testing an integrated circuit package. The integrated circuit
package includes a plurality of daisy chain loops that are
connected to a pair of package pads, wherein adjacent daisy chain
loops are oppositely biased. Aspects of the present invention
include forming a first plurality of gangs of electrically coupled
daisy chain loops having a first bias, and forming a second
plurality of gangs of electrically coupled daisy chain loops having
a second bias. Each one of the first plurality of gangs is
individually coupled to an electrical measurement device, while the
second plurality of gangs are electrically coupled in common, and
the common gang is coupled to the electrical measurement device.
According to the method and system disclosed herein, the electrical
measurement device may be used to indicate whether there is any
leakage between one or more of the first plurality of gangs and the
common gang, thereby eliminating the need to use an ATE tester and
a sophisticated and expensive device under test (DUT) circuit board
to perform reliability tests.
[0008] According to the method and system disclosed herein, the
present invention significantly reduces testing costs, results in
faster test turnaround times, can be used for real time testing,
such as during drying of the test packages in an oven, and enables
testing to be performed at sites where an ATE tester is not readily
available.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a side view of the reliability testing system of
the present invention.
[0010] FIG. 2 is a diagram illustrating a top view of the gang
testing board and electrical connections thereof.
[0011] FIG. 3 is a diagram illustrating a gang testing board having
four edge card connectors.
DETAILED DESCRIPTION OF THE INVENTION
[0012] The present invention relates to a method and apparatus for
testing IC packages. The following description is presented to
enable one of ordinary skill in the art to make and use the
invention and is provided in the context of a patent application
and its requirements. Various modifications to the preferred
embodiments and the generic principles and features described
herein will be readily apparent to those skilled in the art. Thus,
the present invention is not intended to be limited to the
embodiments shown, but is to be accorded the widest scope
consistent with the principles and features described herein.
[0013] The present invention provides a reliability testing system
for testing a daisy chained IC package (hereinafter test packages)
that eliminates the need to use an expensive ATE tester and device
under test (DUT) circuit board to perform reliability tests, such
as leakage and resistance.
[0014] FIG. 1 is a side view of the reliability testing system of
the present invention; and FIG. 2 is a diagram illustrating a top
view of the gang testing board and electrical connections thereof.
Referring to both FIGS. 1 and 2, the reliability testing system 10
is a simplified testing apparatus for performing reliability tests
on a test package 18. The test package 18 includes an array of pads
11, which may be BGA balls or leads, in which pairs of the pads 11
are connected to form daisy chain loops 13. As described above,
adjacent parallel lines (columns or rows) of daisy chain loops 13
are alternately biased positive and negative.
[0015] The test package 18 is mounted to a conventional test socket
20. As is well known in the art, the test socket 20 has
pass-through connections 22 that allow the pads 13 of the test
package 18 to connect to another device or circuit board. In a
preferred embodiment of the present invention, a gang testing board
12 is provided on which the test package 18 is mounted using the
test socket 20.
[0016] This particular gang testing board 12 includes wire fingers
22 and at least two edge card connectors; sectioned edge card
connector 14 and shorted edge card connector 16 mounted along the
sides of the gang testing board 12. According to the present
invention, the wire fingers 24 are coupled to the pads of the test
package 18 via the test socket 20, such that multiple gangs of
positively biased daisy chain loops 30 are formed and multiple
gangs of negatively biased daisy chain loops 32 are formed. As
shown, adjacent gangs 30 and 32 formed by the wire fingers 24 are
oppositely biased.
[0017] The test package 18 may be mounted on the gang testing board
12 such that the positively biased gangs 30 are electrically
connected in parallel to one of the edge card connectors 14 or 16,
and the negatively biased gangs 32 are electrically connected in
parallel to the other edge card connector 14 or 16. The two edge
card connectors 14 and 16 are coupled to an electrical measuring
device 26, such as a data logger system or Kelvin ohm meter, to
measure cumulative leakage between the adjacent lines of daisy
chain loops 13. As an example of the electrical measuring device
26, a 32 channel data logger may be used to test a 1413 pin ball
grid array (BGA) test package.
[0018] In the embodiment shown in FIG. 2, the sectioned edge card
connector 14 makes an electrical connection to each one of the
positively biased gangs 30, while the shorted edge card connector
16 makes an electrical connection to each one of the negatively
biased gangs 32. In a preferred embodiment, the wire fingers 24 are
configured such that approximately two to thirteen gangs are
formed, where each gang includes approximately fifteen daisy chain
loops 13.
[0019] According to the present invention, the sectioned edge card
connector 14 couples each one of the positively biased gangs 30 to
the electrical measuring device 26. In contrast, the shorted edge
card connector 16 electrically shorts each of the negatively biased
gangs 32 together to form one common negatively biased gang 34, and
couples the common negatively biased gang 34 to the electrical
measuring device 26. During testing, the electrical measuring
device 26 indicates whether there is any leakage between one or
more of the positively biased gangs 30 and the common negatively
biased gang 34.
[0020] If the electrical measuring device 26 does not indicate a
leak is present, then the leakage test ends. Approximately 90% or
more of all test packages 18 should pass the leakage test. If the
electrical measuring device 26 does indicate a leak is present,
then the presence of the leak is confirmed by switching positions
of the edge card connectors 14 and 16 on the gang testing board 12.
The test is then repeated with the positively biased gangs 32 held
in common by the shorted edge card connector 16, and individual
negatively biased gangs 34 are input to the electrical measuring
device 26 by sectioned edge card connector 14. In an alternative
embodiment, the test socket 20 with the test package 18 could be
turned around on the gang testing board 12, rather than physically
switching the connectors. However, this would require the presence
of symmetrical connections.
[0021] If a leak is still indicated during the repeated test, then
the electrical measuring device 26 identifies the leaking
negatively biased gang 34. The use of the gang testing board will
not automatically identify the exact failure site. However, this
may be accomplished by manually probing to identify which one of
the daisy chained loops 13 in the identified gang is leaking, or by
ATE testing. In the case where ATE testing is chosen, the present
invention eliminates 90% of the samples requiring ATE testing.
[0022] Utilizing the reliability system 10 of the present
invention, failures can be isolated to the following levels:
[0023] Leak Isolation--Based on 64 contact(32 channel)
[0024] i. For a 2397 pin BGA, 13 loops
[0025] ii. For a 1413 pin BGA, 7 loops
[0026] iii. For a 313 pin BGA, 2 loops
[0027] Open Isolation
[0028] i. For a 2397 pin BGA, 50*-25 loops
[0029] ii. For a 1413 pin BGA, 27*-14 loops *Kelvin
Measurement.
[0030] The reliability testing system using daisy chain gang
testing in accordance with the present invention provides the
following advantages; 1) reduced cost, 2) faster test turnaround,
3) can be used for real time testing, such as during drying of the
test packages in an oven, and 4) testing can be performed at sites
where an ATE tester is not readily available.
[0031] In an alternative embodiment, a gang testing board for
leakage testing may be constructed with edge card connectors on all
four sides. FIG. 3 is a diagram illustrating a gang testing board
having four edge card connectors (A), (B), (C), and (D), thereby
decreasing the number of daisy chain loops in each gang. By using
electrical measuring device 26, such as a simple 32 channel data
logger, for instance, the leakage testing can proceed as
follows:
[0032] In this embodiment, edge card connector (A) is a shorted
edge card connectors that shorts together all negatively biased
gangs, while the other three edge card connectors (B), (C), and (D)
each coupled to respective positively biased gangs of loops. With
edge card connector (A), 32 parallel paths are created, each with
{fraction (1/32)} of one side of the I/O loops, where, all of the
Vss loops are held common.
[0033] For leak test measurements of I/O, measurements are taken
with edge card connector (A). If there is no leaking, then I/O loop
testing is complete. If a leak exists then the above test is
repeated with edge card connector (A) used to short the positively
biased gangs and edge card connectors (B), (C), and (D) coupled to
respectively negatively biased gangs. This will allow
identification of the exact negative to positive biased gang
location. For leak measurement of I/O to planes, each Vdd plane is
represented as a connection finger of the positive biased sectioned
edge card connector, while each Vss plane is represented as a
connection finger of the negatively biased sectioned edge card
connector to determine if the I/O is leaking across the plane
isolation rings.
[0034] In a further embodiment, depending on the application, two
of the four edge card connectors could be shorted edge card
connectors, while the other two are sectioned.
[0035] The use of a shorting edge card connector to allow selective
edge card connections on all four board sides has the ability to
isolate faults with a relatively small number of loops per gang.
Without the shorting edge card connector technique, many more
multiples of single edge card connectors or a sophisticated ATE
would be needed to accomplish the same level of isolation. Thus,
the present invention provides the ability to approach the
isolation achieved with expensive Automated Test Equipment using
equipment costing several orders of magnitude less.
[0036] A reliability testing system using daisy chain gang testing
has been disclosed. The present invention has been described in
accordance with the embodiments shown, and one of ordinary skill in
the art will readily recognize that there could be variations to
the embodiments, and any variations would be within the spirit and
scope of the present invention. Accordingly, many modifications may
be made by one of ordinary skill in the art without departing from
the spirit and scope of the appended claims.
* * * * *