ASTM F1269-89(1995)e1

Test Methods for Destructive Shear Testing of Ball Bonds

SCOPE
1.1 These test methods cover tests to determine the shear strength of a series of ball bonds made by either thermal compression or thermosonic techniques. Note 1Common usage at the present time considers the term "ball bond'' to include the enlarged spheriodal or nailhead portion of the wire, (produced by the flameoff and first bonding operation in the thermal compression and thermosonic process, or both,) the underlying bonding pad, and the ball bond-bonding pad interfacial-attachment area or weld interface.
1.2 These test methods cover ball bonds made with small diameter (from 18 to 76-µm (0.0007 to 0.003-in.)) wire of the type used in integrated circuits and hybrid microelectronic assemblies.
1.3 These test methods can be used only when the ball height and diameter are large enough and adjacent interfering structures are far enough away to allow suitable placement and clearance (above the bonding pad and between adjacent bonds) of the shear test ram.
1.4 These test methods are destructive. They are appropriate for use in process development or, with a proper sampling plan, for process control or quality assurance.
1.5 A nondestructive procedure is possible; although it may be contra indicated due to the possible interference with adjacent wire bonds and microcircuit components.
1.6 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-Dec-2000
• Technical Committee: F01 - Electronics

Relations

• Replaced By: ASTM F1269-89(2001) - Test Methods for Destructive Shear Testing of Ball Bonds
• Effective Date: 01-Jan-2001

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
e1
Designation: F 1269 – 89 (Reapproved 1995)
Test Methods for
Destructive Shear Testing of Ball Bonds
This standard is issued under the fixed designation F 1269; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Keywords were added editorially in June 1995.
1. Scope F 458 Practice for Nondestructive Pull Testing of Wire
Bonds
1.1 These test methods cover tests to determine the shear
F 459 Test Methods for Measuring Pull Strength of Micro-
strength of a series of ball bonds made by either thermal
electronic Wire Bonds
compression or thermosonic techniques.
2.2 NIST Document:
NOTE 1—Common usage at the present time considers the term “ball
NBS Handbook 105-1 Specification and Tolerances for
bond’’ to include the enlarged spheriodal or nailhead portion of the wire,
Reference Standards and Field Standards, Weights and
(produced by the flameoff and first bonding operation in the thermal
Measures
compression and thermosonic process, or both,) the underlying bonding
IOLM Class M2-Circular 547-1 Precision Laboratory Stan-
pad, and the ball bond-bonding pad interfacial-attachment area or weld
dards of Mass and Laboratory Weights
interface.
2.3 Military Standard:
1.2 These test methods cover ball bonds made with small
MIL-STD 883C, Method 2010
diameter (from 18 to 76-μm (0.0007 to 0.003-in.)) wire of the
type used in integrated circuits and hybrid microelectronic
3. Terminology
assemblies.
3.1 Definitions of Terms Specific to This Standard:
1.3 These test methods can be used only when the ball
3.1.1 ball lift—a separation of the ball bond at the bonding
height and diameter are large enough and adjacent interfering
pad interface with little or no residual (less than 25 % of the
structures are far enough away to allow suitable placement and
bond deformation area) ball metallization remaining on the
clearance (above the bonding pad and between adjacent bonds)
bonding pad (that remains essentially intact). In the case of
of the shear test ram.
gold ball bonds on aluminum pad metallization, a ball lift is
1.4 These test methods are destructive. They are appropriate
defined as a separation of the ball bond at the bonding pad
for use in process development or, with a proper sampling plan,
interface with little or no intermetallic formation either present
for process control or quality assurance.
or remaining (area of intermetallic less than 25 % of the bond
1.5 A nondestructive procedure is possible; although it may
deformation area).
be contra indicated due to the possible interference with
3.1.1.1 Discussion—ntermetallic refers to the aluminum
adjacent wire bonds and microcircuit components.
gold alloy formed at the ball bond pad metallization interfacial
1.6 The values stated in SI units are to be regarded as the
area where a gold ball bond is attached to an aluminum pad
standard. The values given in parentheses are for information
metallization.
only.
3.1.2 ball shear (weld interface separation)—an appre-
1.7 This standard does not purport to address all of the
ciable intermetallic (in the case of the aluminum-gold system)
safety concerns, if any, associated with its use. It is the
and ball metallization, or both, (in the case of the gold-to-gold
responsibility of the user of this standard to establish appro-
system) remains on the bonding pad (area of remaining metal
priate safety and health practices and determine the applica-
or intermetallic greater than 25 % of the bond deformation
bility of regulatory limitations prior to use. Fig. 1Fig. 2Fig.
area).
3Fig. 4Fig. 5Fig. 6Fig. 7Fig. 8Fig. 9
3.1.3 bonding pad lift (substrate metallization removal)—a
separation between the bonding pad and the underlying sub-
2. Referenced Documents
strate. The interface between the ball bond and the residual pad
2.1 ASTM Standards:
metallization attached to the ball remains intact.
These test methods are under the jurisdiction of ASTM Committee F-1 on
Electronics and is the direct responsibility of Subcommittee F01.07 on Wire
Annual Book of ASTM Standards, Vol 10.04.
Bonding.
Current edition approved Dec. 29, 1989. Published March 1990. Available from the National Technical Information Service, 5285 Port Royal
Panousis, N. T., and Fischer, M. W., “Nondestructive Shear Testing of Ball Rd., Springfield, VA 22161.
Bonds’’, International Journal of Hybrid Microelectronics, Vol 6, No. 1, 1983, p. Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700
142. Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
F 1269
FIG. 1 Ball Shear Failure Modes
3.1.4 cratering—bonding pad lifts taking a portion of the cratering. Cratering caused prior to the shear test operation is
underlying substrate material with it. Residual pad and sub- unacceptable.
strate material are attached to the ball. The interface between Various aspects of the failure mode definitions are illustrated
the ball and this residual material remains intact. in Fig. 1.
3.1.4.1 Discussion—It should be noted that cratering can be
4. Summary of Test Methods
caused by several factors including the ball bonding operation,
the post-bonding processing, and even the act of shear testing 4.1 The microelectronic device with the ball bond (wire
itself. If cratering occurs, chemically etch off the ball bonds bond (see Practice F 458 and Test Methods F 459)) to be tested
and bond pads of untested units and microscopically check for is held firmly in an appropriate fixture. A shearing ram is
F 1269
NOTE 1—Schematic diagrams of the ball shear test. (A) Horizontal sample and horizontal ram. (B) Horizontal sample and vertical ram. (C) Vertical
sample and vertical ram. The bonded (welded) area may be less than the interfacial contact area (area of intimate contact as observed optically.) Typical
dimensions with 25-μm (1-mil) diameter wire are: ball diameter 75 to 110 μm (3.0 to 4.5 mil) and ball height 25 μm (1 mil) or less.
FIG. 2 Ball Shear Test Configurations
positioned parallel to the substrate and approximately 25 μm (1 5. Significance and Use
mil) above the substrate metallization. A typical shearing
5.1 Failure of microelectronic devices is often due to the
configuration is shown in Fig. 2. The ram is then moved into
failure of an interconnection bond. A common type of inter-
the ball until the ball separates from the substrate. The force
connection bond is the thermo compression or thermosonic
applied to the ram, in order to cause the failure of the ball bond,
gold wire bond. A very important element of this interconnec-
is recorded. The mode of failure (for example, ball lift,
tion is the first bond or ball bond. These test methods can assist
weld-interface separation, cratering, etc.) is observed and
in maintaining control of the process for making ball bonds.
recorded.
They can be used to distinguish between weak and nonadherent
NOTE 2—Bonds made with larger diameter wire may require that the
ball bonds, of both, and bonds that are acceptably strong.
ram be placed further above the substrate, but in all cases the ram should
5.2 These test methods are appropriate for on-line use in
be located below the ball’s horizontal centerline. The distance below the
process control, for process development, for purchase speci-
center should be at least half the distance between the center line and the
fications, and for research in support of improved yield and
substrate.
reliability. Since the ball shearing method tests only the first
NOTE 3—Besides ball separation from the substrate, other modes of
failure are possible and will be described in Section 6. bond in a microelectronic wire bond interconnection system, it
F 1269
FIG. 3 Ball Shear Interferences
6,7
must be used in a complementary fashion with the wire bond 6.4 In bonding systems in which excessive intermetallic
pull test. growth has formed around the ball bond, the shearing ram may
contact the intermetallic rather than the ball bond and thus the
6. Inferences
shear readings can be in error (that is, weak ball bond shear is
masked by the shear strength of the strong intermetallic wreath
6.1 The most common interference is wire shear in which
surrounding it.
the ball is sheared too high or offline. Only a minor fragment
of the ball is attached to the wire. The major portion of the ball
7. Apparatus
remains on the pad with the bond-pad weld interface region
7.1 Ball Bond Shearing Machine—Apparatus for measuring
intact. Wire shear is illustrated in Fig. 1, View B.
6.2 Many of the common interference modes (such as wire the ball bond shear strength are required with the following
components:
shear) are caused by improper positioning of the ram during the
ball shear operation as shown in Fig. 3. Rams that are too high 7.1.1 Shearing Ram—Various shearing tools or rams have
been recommended in the technical literature, but the ones that
(Fig. 3, View B) or angled upward (Fig. 3, View D) result in
lower than normal shear strength values. Rams that are angled appear the most effective have a flat chisel shape with a
shearing edge dimension equal to approximately 1 to 2-ball
downward (Fig. 3, View C and Fig. 4) or positioned too low
(Fig. 3, View A) will strike the bonding pad and the substrate, diameters as shown in Fig. 5. For 25.4-μm (1-mil) diameter
wire this dimension would be approximately 0.152 mm (6
or both, (chip) and cause inordinately high shear strength as
well as potentially damage the shearing ram. mils).
7.1.2 Shearing and Gaging Mechanism—Mechanism for
6.3 Shearing gold ball bonds on gold metallization pads or
substrates can lead to friction rewelding as illustrated in Fig. 4. applying a measured vertical (or horizontal) force to the
As a strongly welded gold bond is sheared, the ball tends to tip shearing is needed. The mechanism shall incorporate a means
for recording maximum force applied and shall be capable of
away from the ram and contact the substrate as it moves. The
ball smears against the pad metallization and rewelds itself applying the shear force at a uniform rate of ram motion. Force
application rate can be variable (either continuously or in fixed
often several times before it finally clears the metallization.
steps) to accommodate different shearing conditions and con-
figurations, or both. In no case should the ram speed exceed 6.0
mm/s.
Charles, Jr., H. K., and Clatterbaugh, G. V., “Ball Bond Shearing—A
Complement to the Wire Bond Pull Test’’, International Journal of Hybrid
NOTE 4—It has been shown that the shear force is independent of force
Microelectronics, Vol 6, No. 1, 1983, p. 171.
application rate in the range from 0.25 to 6.0 mm/s.
Harman, G. G. “The Microelectronic Ball-Bond Shear Test—A Critical Review
NOTE 5—Electronic-strain gage-force reading mechanisms are pre-
and Comprehensive Guide to its Use’’, International Journal of Hybrid Microelec-
tronics, Vol 6, No. 1, 1983, p. 127. ferred; however, the dynamometer type mechanisms known as“ gram
F 1269
FIG. 4 Gold-to-Gold Friction Rewelding
gages’’ may be used satisfactorily providing careful calibration test
mechanism for calibration, are needed. In the case of horizontal
procedures are employed.
shearing ram motion, the tester mechanism should rotate 90° to
allow the weights to be hung from the shearing ram. Other
7.1.2.1 The range of the force reading gage shall be selected
indirect methods of calibration may also be possible for this
so that the maximum scale reading will be no greater than three
configuration.
times the expected average ball bond shear strength. Antici-
7.1.6 Shear Test Tolerances—The shear test sample holder
pated force ranges for the various wire sizes and materials
covered by these test methods are summarized in Fig. 6. or the shear test ram must be able to be positioned to tolerances
better than 610 μm (6 0.4 mils) and the X and Y directions
NOTE 6—The maximum scale range of the electronic strain gage with
(plane of the bonding pad) and 5.0 μm (60.2 mils) in the Z or
digital readout may be larger than three times the expected average shear
the above substrate direction. The shearing rams over travel
strength providing the accuracy specified in 10.7.6 is maintained over the
(distance it proceeds from the point of ball contact) should be
entire range of the load cell.
limited to 2-ball diameters. Additional over travel may be
7.1.3 Microscope and Light Source—Zoom microscope
allowed in cases where the excessive ram motion does not
with a light source for viewing the device under test is needed.
damage other bonds or the device under test.
The minimum magnification shall be at least 603.
7.2 Typical shear test configurations are illustrated in Fig. 7.
7.1.4 Device Holder— A clamping mechanism for rigidly
View a shows a horizontal test system with horizontal shearing
holding the device under test in either a horizontal or vertical
ram motion. View b presents a vertical test system with vertical
position depending upon shear tester configuration is required
shearing ram motion.
(see 7.2).
7.1.5 Calibration Masses—At least five masses (weights)
8. Sampling
with mass values known to an accuracy of 0.5 % (or better,
such as NBS Class T or IOLM Class M2 (NBS Handbook 8.1 Since the shear test method is destructive, it shall be
105-1 and Circular 547. IOLM) ) sized to cover the shearing performed on a sampling basis. The sample selected should be
and gaging mechanism range of force measurements and representative of the ball bonds of interest. The size of the
suitably configured so that they may be supported by the shear sample and the method of selection shall be agreed upon by the
F 1269
FIG. 6 Shear Force Versus Diameter of the Bonded Area for
Various Wire Materials and Sizes
NOTE 1—Tool face is 1 to 2 ball diameters.
FIG. 5 Schematic Representation of Shearing Tool 25.4μμμ m
Diameter Wire
parties to the test. The sample space should be as large as
practical (nominally 35 bonds) to ensure the proper statistical
inferences from quantities such as the mean shear force (X)
and its standard deviation (s).
9. Calibration
9.1 Calibrate the ball bond shearing machine at the begin-
ning and of each series of tests, or at the beginning and end of
each day if the test sequence spans more than one day.
9.2 For multifunct
...