1、JEDEC STANDARD Wire Bond Shear Test Method JESD22-B116B (Revision of JESD22-B116A, August 2009) APRIL 2017 JEDEC SOLID STATE TECHNOLOGY ASSOCIATION NOTICE JEDEC standards and publications contain material that has been prepared, reviewed, and approved through the JEDEC Board of Directors level and s
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9、0th Street Suite 240 South Arlington, VA 22201-2107 or refer to www.jedec.org under Standards-Documents/Copyright Information. JEDEC Standards No. 22-B116B Page 1 Test Method B116B Revision of Test Method B116A TEST METHOD B116B WIRE BOND SHEAR TEST (From JEDEC Board Ballot JCB-17-10, formulated und
10、er the cognizance of the JC-14.1 Subcommittee on Reliability Test Methods for Packaged Devices.) 1 Scope This test provides a means for determining the strength of a ball bond to a die or package bonding surface, and may be performed on pre-encapsulation or post-encapsulation devices. This measure o
11、f bond strength is extremely important in determining two features: 1) the integrity of the metallurgical bond which has been formed, and 2) the quality of ball bonds to die or package bonding surfaces. This test method covers thermosonic (ball) bonds made with small diameter wire from 15 m to 76 m
12、(0.6 mil to 3.0 mil). This test method can only be used when the bonds are large enough to allow for proper contact with the shear test chisel and when there are no adjacent interfering structures that would hinder the movement of the chisel. For consistent shear results the ball height must be at l
13、east 4.0 m (0.16 mils) for ball bonds, which is the current state of the art for bond shear test equipment at the time of this revision. This test method can also be used on ball bonds that have had their wire removed and on to which a 2ndbond wire (typically a stitch bond) is placed. This may be kn
14、own as “stitch on ball” and “reverse bonding”. See Annex A for additional information. The wire bond shear test is destructive. It is appropriate for use in process development, process control, and/or quality assurance. This test method may be used on ultrasonic (wedge) bonds, however its use has n
15、ot been shown to be a consistent indicator of bond integrity. See Annex B for information on performing shear testing on wedge bonds. JEDEC Standards No. 22-B116B Page 2 Test Method B116B Revision of Test Method B116A 2 Terms and definitions For the purposes of this standard, the following terms and
16、 definitions apply: 2.1 ball bond: The adhesion or welding of a small diameter wire, typically gold or copper, to a bonding surface metallization, usually an aluminum alloy, using a thermosonic wire bond process. NOTE 1 The ball bond includes the enlarged spherical, or nail-head, portion of the wire
17、 (provided by the flame-off and first bonding operation), the underlying bonding surface and the ball bond-bonding surface metallurgical weld interface. NOTE 2 Gold wire implies a gold alloy in which the gold content is likely 99% or greater. Copper wire implies a copper alloy of similarly high copp
18、er content and also includes copper wire with a very thin coating of palladium. NOTE 3 At the time of this revision, other wire materials and wire coatings are being evaluated, but there is not enough information collected to confirm that the fail modes listed in this test method are valid for any o
19、f the new wire types. 2.2 bonding surface: Either 1) the die pad metallization or 2) the package surface metallization to which the wire is ball bonded. 2. bond shear: A process in which an instrument uses a chisel-shaped tool to shear or push a ball bond off the bonding surface (see Figure 1). NOTE
20、 The force required to cause this separation is recorded and is referred to as the bond shear force. The bond shear force of a ball bond, when correlated to the diameter of the ball bond, is an indicator of the quality of the metallurgical bond between the ball bond and the bonding surface metalliza
21、tion. Figure 1 Bond shear set-up for bond on die bonding pad (Similar setup for bonds on other bonding surfaces, such as package substrate/leadframe) JEDEC Standards No. 22-B116B Page 3 Test Method B116B Revision of Test Method B116A 2 Terms and definitions (contd) 2.4 shear tool; shear arm: A chise
22、l (made of tungsten carbide or an equivalent material with similar mechanical properties) with specific angles on the bottom and back of the tool to ensure a shearing action. 2.5 stitch bond: The second bond during the ball (thermosonic) bonding process, in which the wire is typically bonded to the
23、package bonding surface. NOTE 1 A stitch bond may also be referred to as a crescent bond. NOTE 2 For some unique constructions (e.g., “stitch on ball”), the second bond may be formed on top of another ball bond, from which the wire has been removed. 2.6 wedge bond: The adhesion or weld of a thin wir
24、e, typically aluminum, copper, or gold to a die pad metallization or the package bonding surface, usually a plated leadframe post or finger, using an ultrasonic wire bonding process. NOTE See Annex B for information on performing shear testing on wedge bonds. 3 Apparatus and material The apparatus a
25、nd materials required for bond shear shall be as follows: 3.1 Inspection equipment An optical microscope system or scanning electron microscope providing a minimum of 70X magnification. A higher magnification may be necessary for 15 m (0.6 mil) diameter wire. 3.2 Measurement equipment An optical mic
26、roscope/measurement system capable of measuring the bond diameter to within 2.54 m (0.10 mil). 3.3 Workholder Fixture used to hold the part being tested parallel to the shearing plane and perpendicular to the shear tool. The fixture shall also eliminate part movement during bond shear testing. If us
27、ing a caliper controlled workholder, place the holder so that the shear motion is against the positive stop of the caliper. This is to ensure that the recoil movement of the caliper controlled workholder does not influence the bond shear test. JEDEC Standards No. 22-B116B Page 4 Test Method B116B Re
28、vision of Test Method B116A 3.4 Bond shear equipment The bond shear equipment must be capable of repeatable, precision placement of the shearing tool with respect to the ball height and the bonding surface. The specified distance (h) above the topmost part of the bonding surface (e.g., passivation l
29、ayer on IC, solder mask on organic substrate) shall ensure the shear tool does not contact the bonding surface (e.g., top passivation or polyimide layer, soldermask) and shall be less than the distance from the topmost part of the bonding surface to the center line (CL) of the ball bond (see Figure
30、2). See Annex C for guidance when the passivation, or other structures on the die surface and excessive Al splash prevent the shear tool from contacting the ball below the center line. The ball height Center Line is the distance from the top of the ball to the top of the bonding surface CLhPassivati
31、onlayerFigure 2 Proper height placement of shear tool with respect to ball center line 3.5 Bond shear chisel tool setup When choosing the proper chisel for the bond being sheared items to consider include but are not limited to: flat shear face, sharp shearing edge, shearing width of a minimum of 1.
32、2X the bond diameter, and bond length. The sample and chisel face should be clean and free of chips or other defects that will interfere with the shearing test. Bonds should also be examined to determine if adjacent interfering structures are far enough away to allow suitable placement and clearance
33、 (above the bonding surface and between adjacent bonds) for the shear test tool. JEDEC Standards No. 22-B116B Page 5 Test Method B116B Revision of Test Method B116A 4 Procedure 4.1 Calibration Before performing the bond shear test, it must be determined that the equipment has been calibrated in acco
34、rdance with manufacturers specifications and is presently in calibration. Recalibration is required if the equipment is moved to another location. 4.2 Visual examination of bonds to be tested after decapsulation In addition to being a manufacturing process monitor, this test method can also be used
35、to assess bond strength of encapsulated devices after soldering operations or after reliability stress testing. To do this, the encapsulation material needs to be removed in a manner that does not significantly degrade the wire, the bond, the bonding interface, or the bonding surface. Shear force va
36、lues are often lower for bonds that have been decapsulated, and therefore cannot be compared to values for similar, unencapsulated bonds. If the decapsulation process is well controlled and repeatable, which is the case for gold wire, then this test method can be used for lot to lot comparison; howe
37、ver, it may be hard to consistently control the decapsulation process for copper wires to ensure the accuracy of the results. For Cu wires, the effectiveness of etch has been seen to vary due to the encapsulation material and the level of reliability stress testing performed on the samples. See Anne
38、x D for additional information regarding the decapsulation process of devices with Cu wire bonds. Bonds must also be examined to determine that enough encapsulation material has been removed to allow suitable placement and clearance (above the bonding surface and between adjacent bonds) for the shea
39、r test tool. 4.2.1 Bond pad examination and acceptability criteria for both Al and Cu bond pad metallization If performing bond shear testing on a device which has been opened using wet chemical and/or dry etch techniques, the bond pads shall be examined to ensure there is no absence of metallizatio
40、n on the bonding surface area due to chemical etching, and wire bonds are attached to the bonding surface. Those bonds on Al or Cu bond pads with significant chemical attack or absence of metallization shall not be used for ball shear testing. The shear results for any damaged bonds found during pos
41、t shear inspection may also be excluded. It is possible that wire bonds on bonding surfaces without degradation from chemical attack may not be attached to the bonding surface due to other causes (e.g., package stress). These wire bonds are considered valid and shall be included in the shear data as
42、 a zero (0) shear force value. 4.2.2 Copper bond and Cu wire examination and acceptability criteria If performing bond shear testing on a part with copper wires, the Cu bond and Cu wire shall be examined before or after the shear test to ensure there is no significant loss of metal or other damage d
43、ue to decapsulation process that might affect the results of the shear test. The shear result can be excluded for a Cu bond or Cu wire with significant chemical attack or other damage due to the decapsulation process. Annex D provides additional information to assess what level of damage is acceptab
44、le. JEDEC Standards No. 22-B116B Page 6 Test Method B116B Revision of Test Method B116A 4.3 Measurement of the ball bond diameter to determine the ball bond shear failure criteria Once the bonding surfaces have been examined and before performing bond shear testing, the diameter of all ball bonds to
45、 be tested shall be measured and recorded. The ball is measured at the widest point of the ball bond. For symmetrical ball bonds (those basically round) only one measurement per bond needs to be taken. For asymmetrical bonds, determine the average diameter using both the largest (dlarge) and the sma
46、llest (dsmall) diameter values (see Figure 3). These two ball bond diameter measurements shall be used to determine the mean, or average, diameter value. The resulting mean, or average, ball bond diameter shall then be used to establish the failure criteria as defined in bond shear qualification sta
47、ndards. Diameter Measured at widest point of the ball SYMMETRICAL ASYMMETRICAL Figure 3 Ball bond measurement: side view and top view (for symmetrical vs. asymmetrical) To determine whether the sheared bond has passed the acceptability criteria that is stated in JESD47, the shear force must be divid
48、ed by the ball bond area. The equation for area is: A = r2= (d)2/4 Where d is the above measured diameter (or mean diameter for an asymmetrical ball bond) for the bond being sheared. To facilitate faster testing a statistically representative ball bond diameter may be used with all of the bonds shea
49、red within a sample when calculating the shear force per unit area for each bond sheared (in lieu of using the corresponding ball diameter for each ball sheared to calculate its shear force per unit area value). JEDEC Standards No. 22-B116B Page 7 Test Method B116B Revision of Test Method B116A 4.4 Performing the bond shear test The bond shear equipment shall pass all self-diagnostic tests before beginning the test. The bond shear equipment and test area shall be free of excessive vibration or movement. Examine the shear tool to verify it is in good
