JEDEC JESD22-B116A-2009 Wire Bond Shear Test Method.pdf

1、JEDEC STANDARD Wire Bond Shear Test Method JESD22-B116A (Revision of JESD22-B116, July 1998) AUGUST 2009 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 sub

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9、may obtain permission to reproduce a limited number of copies through entering into a license agreement. For information, contact: JEDEC Solid State Technology Association 3103 North 10th Street Suite 240 South Arlington, VA 22201-2107 or call (703) 907-7559 JEDEC Standards No. 22-B116A Page 1 Test

10、Method B116A Revision of Test Method B116 TEST METHOD B116A WIRE BOND SHEAR TEST (From JEDEC Board Ballot JCB-09-62, formulated under 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 gol

11、d ball bond to a die bonding surface or an aluminum wedge or stitch bond to a die or package bonding surface, and may be performed on pre-encapsulation or post-encapsulation parts. This measure of bond strength is extremely important in determining two features: 1) the integrity of the metallurgical

12、 bond which has been formed. 2) the quality of gold and aluminum wire bonds to die or package bonding surfaces. These test methods cover ball bonds made with small diameter (from 18 to 76 m, or from 0.7 to 3 mil) wire and wedge bonds made with larger diameter (minimum of 3 mil) wire, of the type use

13、d in integrated circuits and hybrid microelectronic assemblies. These test methods can be used only when the ball height (at least 10.16 m or 0.4 mil) and diameter for ball bonds, or the wire height (at least 1.25 mils in height at the compressed bonded area) of the wedge bond, are large enough and

14、adjacent interfering structures are far enough away to allow suitable placement and clearance (above the bonding pad or leadframe post and between adjacent bonds) of the shear test chisel. This test method may also apply to gold wedge or stitch bonds if the wire is thick enough to allow shearing of

15、the wire from the bonding surface without smearing similar to a shearing skip. The wire bond shear test is destructive. It is appropriate for use in process development, process control and/or quality assurance. 2 Terms and definitions For the purposes of this standard, the following terms and defin

16、itions apply: 2.1 ball bond: The adhesion or welding of a thin wire, usually gold, to a die pad metallization, usually an aluminum alloy, using a thermosonic wire bond process. NOTE The ball bond includes the enlarged spherical, or nail-head, portion of the wire (provided by the flame-off and first

17、bonding operation in the thermal compression and thermosonic process, or both), the underlying bonding pad and the ball bond-bonding pad intermetallic weld interface. 2.2 bond footprint (of a wedge bond): The area of the wire that has a physical bond interface (intermetallic or recrystallized) with

18、respect to the compressed area of the wire. JEDEC Standards No. 22-B116A Page 2 Test Method B116A Revision of Test Method B116 2 Terms and definitions (contd) 2.3 bonding surface: Either 1) the die pad metallization or 2) the package surface metallization to which the wire is ball-, wedge-, or stitc

19、h-bonded. 2.4 bond shear: A process in which an instrument uses a chisel-shaped tool to shear or push a ball or wedge bond off the bond pad (see Figure 1). NOTE The force required to cause this separation is recorded and is referred to as the bond shear force. The bond shear force of a gold ball bon

20、d, when correlated to the diameter of the ball bond, is an indicator of the quality of the metallurgical bond between the gold ball bond and the bond pad metallization. The bond shear force of an aluminum wedge bond, when compared to the manufacturers tensile strength of the wire, is an indicator of

21、 the integrity of the weld between the aluminum wire and the bond pad or package surface metallization. Figure 1 Bond shear set-up 2.5 bond shear codes for ball and wedge bonds (see Figure 2) 2.5.1 Type 1 - bond lift: A separation of the entire wire bond from the bonding surface with only an imprint

22、 being left on the bonding surface and very little evidence of intermetallic formation or welding or of disturbance of the bonding surface metallization. NOTE A bond lift may require an assessment of the bonder settings. 2.5.2 Type 2 - bond shear: A separation of the wire bond where 1) a thin layer

23、of the bonding surface metallization remains with the wire bond and an impression is left in the bonding surface, 2) intermetallics remain on the bonding surface and with the wire bond, or 3) a major portion of the wire bond remains on the bonding surface. JEDEC Standards No. 22-B116A Page 3 Test Me

24、thod B116A Revision of Test Method B116 2 Terms and definitions (contd) 2.5 bond shear codes for ball and wedge bonds (see Figure 2) (contd) 2.5.3 Type 3 cratering: A condition under the die pad metallization in which the insulating layer (oxide or interlayer dielectric) and the bulk material (silic

25、on) separate or chip out. NOTE 1 Separation interfaces that show pits or depressions in the insulating layer (not extending into the bulk) are not considered craters. NOTE 2 Cratering can be caused by several factors including the wire bonding operation, the post-bonding processing, and even the act

26、 of shear testing itself. NOTE 3 Cratering present prior to the shear test operation denotes a pre-existing condition that must be addressed. Any bonds with preexisting cratering are invalid for this test method and shall not be included with the shear data. 2.5.4 Type 4 - arm contacts specimen (bon

27、ding surface contact): The shear tool contacts the bonding surface to produce an invalid shear value. NOTE This condition may be due to improper placement of the specimen, a low shear height, or instrument malfunction. This bond shear type is an invalid result and shall be eliminated from the shear

28、data. 2.5.5 Type 5 - shearing skip: The shear tool removes only the topmost portion of the ball or wedge bond. NOTE This condition may be due to improper placement of the specimen, a high shear height or instrument malfunction. This bond shear type is an invalid result and shall be eliminated from t

29、he shear data. 2.5.6 Type 6 - bond pad (or bonding surface) lift: A separation between the bonding surface metallization and the underlying substrate or base material with evidence of bonding surface metallization remaining attached to the ball or wedge bond. JEDEC Standards No. 22-B116A Page 4 Test

30、 Method B116A Revision of Test Method B116 2 Terms and Definitions (contd) 2.5 Definition of Bond Shear Codes for Ball and Wedge Bonds (see Figure 2) (contd) Bonding surface Wire bond separated from bonding Major portion of wire bond Ball or Wedge bonding weld area intact. Residual bonding surface a

31、nd attached to wire bond. Bonding surface lifted taking portion of substrate (bulk) material. Arm contacted bonding surface metallization Bonding surface separated from die surface. Bonding surface metallization separated from die surface. Minor portion of wire bond attached to wire. Wire bond shear

32、ed too high. Only portion of TYPE 1: Bond Lift TYPE 2: Bond Shear - Gold/Aluminum TYPE 4: Bonding Surface Contact TYPE 3: Cratering TYPE 5: Shearing Skip TYPE 6: Bonding Surface Lift surface. Little or NO intermetallic wire bond removed. on bonding surface. intact. attached to wire. substrate (bulk)

33、 material instead of wire bond. Underlying bonding pad, and the ball bond-bonding pad intermetallic weld interfaceFigure 2 Bond Shear Codes Examples shown here are for ball bonds. These same modes also apply to wedge stitch bonds. JEDEC Standards No. 22-B116A Page 5 Test Method B116A Revision of Tes

34、t Method B116 2 Terms and Definitions (contd) 2.6 shear tool; shear arm: A tungsten carbide, or equivalent, chisel with specific angles on the bottom and back of the tool to ensure a shearing action. 2.7 wedge bond; stitch bond: The adhesion or weld of a thin wire, usually aluminum, to a package bon

35、ding surface, usually a plated leadframe post or finger, using an ultrasonic wire bonding process. NOTE The wedge bond includes the compressed (ultrasonically bonded) area of the wire and the underlying bonding surface. For bonding to an aluminum alloy die bond pad, there is no wedge bond-bond pad i

36、ntermetallic because the two materials are of the same composition, but the two materials are recrystallized together by the ultrasonic energy of the welding process. 3 Apparatus and material The apparatus and materials required for bond shear shall be as follows: 3.1 Inspection Equipment An optical

37、 microscope system or scanning electron microscope providing a minimum of 70X magnification. 3.2 Measurement Equipment An optical microscope/measurement system capable of measuring the bond diameter to within 0.0001 inch (0.1 mil). 3.3 Workholder Fixture used to hold the part being tested parallel t

38、o the shearing plane and perpendicular to the shear tool. The fixture shall also eliminate part movement during bond shear testing. If using 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 movem

39、ent of the caliper controlled workholder does not influence the bond shear test. 3.4 Bond Shear Equipment The bond shear equipment must be capable of precision placement of the shearing tool (2.54m or 0.10 mil) above the substrate. The specified distance (h) above the topmost part of the bonding sur

40、face shall ensure the shear tool does not contact the surface of the die and shall be less than the distance from the topmost part of the bonding surface to the center line (CL) of the ball or wedge bond. 3.5 Bond Shear Tool Required shear tool parameters include but are not limited to: flat shear f

41、ace, sharp shearing edge, shearing width of a minimum of 1.2X the bond diameter, or bond length. The shearing tool should be designed so as to prevent ploughing and drag during testing. The tool should be clean and free of chips or other defects that will interfere with the shearing test. JEDEC Stan

42、dards No. 22-B116A Page 6 Test Method B116A Revision of Test Method B116 4 Procedure 4.1 Calibration Before performing the bond shear test, it must be determined that the equipment has been calibrated in accordance with manufacturers specifications and is presently in calibration. Recalibration is r

43、equired if the equipment is moved to another location. 4.2 Visual Examination of Bonds to be Tested After Decapsulation If performing bond shear testing on a part 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 met

44、allization on the bonding surface area due to chemical etching, and wire bonds are attached to the bonding surface. Those ball or wedge bonds on bond pads with significant chemical attack or absence of metallization shall not be used for ball shear testing. It is possible that wire bonds on bonding

45、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 a zero (0) gram value. Bonds must also be examined to determine if adjacent interf

46、ering structures are far enough away to allow suitable placement and clearance (above the bonding surface and between adjacent bonds) for the shear test tool. 4.3 Sample Sizes Sample sizes shall be a minimum specified by SPC controls in effect for specific processes, or as specified in the applicabl

47、e procurement document 4.4 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 be tested shall be measured and recorded. For asymmetrical bonds

48、, determine the average using both the largest (dlarge) and the smallest (dsmall) diameter values (see Figure 3). These 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

49、the failure criteria as defined in Figure 4 and Table 1. If process monitor data has established the nominal ball bond diameter, then that value may be used to determine the failure criteria as defined in Figure 4 and Table 1. JEDEC Standards No. 22-B116A Page 7 Test Method B116A Revision of Test Method B116 4 Procedure (contd) 4.4 Measurement of the Ball Bond Diameter to Determine the Ball Bond Shear Failure Criteria (contd) SYMMETRICAL ASYMMETRICAL Figure 3 Ball bond measurement (symmetrical vs. asymmetrical) MINIMUM SHEAR VALUESBALL