1、Designation: F1269 13Standard Test Methods forDestructive Shear Testing of Ball Bonds1This standard is issued under the fixed designation F1269; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in
2、 parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover tests to determine the shearstrength of a series of ball bonds made by either thermosonicor thermal compression techniq
3、ues using either gold or copperwires.NOTE 1Common usage at the present time considers the term “ballbond to include the enlarged spheriodal or nailhead portion of the wire,(produced by the flameoff/spark EFO and first bonding operation in thethermosonic or thermal compression process), and the ball
4、bond-bonding pad interfacial-attachment area or weld interface.1.2 These test methods cover ball bonds made with smalldiameter (from 18 to 76-m (0.0007 to 0.003-in.) gold orcopper wire of the type used in integrated circuits and hybridmicroelectronic assemblies, system on a chip, and so forth.1.3 Th
5、ese test methods can be used only when the ballheight and diameter are large enough and adjacent interferingstructures are far enough away to allow suitable placement andclearance (above the bonding pad and between adjacent bonds)of the shear test ram.1.4 These test methods are destructive. They are
6、 appropriatefor use in process development or, with a proper sampling plan,for process control or quality assurance.1.5 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.6 This standard does not purport to address all of thesaf
7、ety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2F458 Practice for Nondestructiv
8、e Pull Testing of Wire BondsF459 Test Methods for Measuring Pull Strength of Micro-electronic Wire Bonds2.2 NIST Documents:3NBS Handbook 105-1 Specification and Tolerances for Ref-erence Standards and Field Standards, Weights and Mea-suresIOLM Class M2-Circular 547-1 Precision Laboratory Stan-dards
9、of Mass and Laboratory Weights2.3 Military Standard:4MIL-STD 883, Method 20103. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 ball lifta separation of the ball bond at the bondingpad interface with little or no residual (less than 25 % of thebond deformation area) ball metalliz
10、ation remaining on thebonding pad (that remains essentially intact). In the case ofgold ball bonds on aluminum pad metallization, a ball lift isdefined as a separation of the ball bond at the bonding padinterface with little or no intermetallic formation either presentor remaining (area of intermeta
11、llic less than 25 % of the bonddeformation area).3.1.1.1 DiscussionIntermetallic refers to the aluminumgold alloy formed at the ball bond pad metallization interfacialarea where a gold ball bond is attached to an aluminum padmetallization. If the wire/ball is of copper, then the aluminumintermetalli
12、c is normally much thinner and may not be opti-cally observable.3.1.2 ball shear (weld interface separation) an appre-ciable intermetallic (in the case of the aluminum-gold system)and ball metallization, or both, (in the case of the gold-to-goldsystem) remains on the bonding pad (area of remaining m
13、etalor intermetallic greater than 25 % of the bond deformationarea).3.1.3 bonding pad lift (substrate metallization removal)aseparation between the bonding pad and the underlying sub-strate. The interface between the ball bond and the residual padmetallization attached to the ball remains intact.1Th
14、ese test methods are under the jurisdiction of ASTM Committee F01 onElectronics and is the direct responsibility of Subcommittee F01.07 on WireBonding, Flip Chip, and Tape Automated Bonding.Current edition approved Jan. 1, 2013. Published January 2013. Originallyapproved in 1989. Last previous editi
15、on approved in 2006 as F126906. DOI:10.1520/F1269-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Availab
16、le from the National Technical Information Service, 5285 Port RoyalRd., Springfield, VA 22161.4Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Cons
17、hohocken, PA 19428-2959. United States13.1.4 crateringbonding pad lifts taking a portion of theunderlying substrate material with it. Residual pad and sub-strate material are attached to the ball. The interface betweenthe ball and this residual material remains intact.3.1.4.1 DiscussionIt should be
18、noted that cratering can becaused by several factors including the ball bonding operation,the post-bonding processing, and even the act of shear testingitself. If cratering occurs, chemically etch off the ball bondsand bond pads of untested units and microscopically check forcratering. Cratering cau
19、sed prior to the shear test operation isunacceptable.Various aspects of the failure mode definitions are illustratedin Fig. 1.4. Summary of Test Methods4.1 The microelectronic device with the ball bond (wirebond (see Practice F458 and Test Methods F459) to be testedis held firmly in an appropriate f
20、ixture. A shearing ram isFIG. 1 Ball Shear Failure ModesF1269 132positioned parallel to the substrate and approximately 25 m (1mil) above the substrate metallization (except for the case offine pitch bond bonds and pads, where the ram height can belower, depending on the pitch, final ball height,5an
21、d so forth.A typical shearing configuration is shown in Fig. 2. The ram isthen moved into the ball until the ball separates from thesubstrate. The force applied to the ram, in order to cause thefailure of the ball bond, is recorded. The mode of failure (forexample, ball lift, weld-interface separati
22、on, cratering, etc.) isobserved and recorded.NOTE 2Bonds made with larger or smaller diameter wire may requirethat the ram be placed further above the substrate, or lower, but in all casesthe ram should be located below the balls horizontal centerline. Thedistance below the center should be at least
23、 half the distance between thecenter line and the substrate.NOTE 3Besides ball separation from the substrate, other modes offailure are possible and will be described in Section 6.5. Significance and Use5.1 Failure of microelectronic devices is often due to thefailure of an interconnection bond. The
24、 most common type ofinterconnection bond is the thermosonic gold or copper wirebond. A very important element of this interconnection is thefirst bond or ball bond. These test methods can assist inmaintaining control of the process for making ball bonds. Theycan be used to distinguish between weak a
25、nd nonadherent ballbonds, of both, and bonds that are acceptably strong.5.2 These test methods are appropriate for on-line use inprocess control, for process development, for purchasespecifications, and for research in support of improved yieldand reliability. Since the ball shearing method tests on
26、ly thefirst bond in a microelectronic wire bond interconnectionsystem, it must be used in a complementary fashion5,6with thewire bond pull test.36. Inferences6.1 The most common interference is wire shear in whichthe ball is sheared too high or offline. Only a minor fragmentof the ball is attached t
27、o the wire. The major portion of the ballremains on the pad with the bond-pad weld interface regionintact. Wire shear is illustrated in Fig. 1, View B.6.2 Many of the common interference modes (such as wireshear) are caused by improper positioning of the ram during theball shear operation as shown i
28、n Fig. 3. Rams that are too high(Fig. 3, View B) or angled upward (Fig. 3, View D) result inlower than normal shear strength values. Rams that are angleddownward (Fig. 3, View C and Fig. 4) or positioned too low(Fig. 3, View A) will strike the bonding pad and the substrate,or both, (chip) and cause
29、inordinately high shear strength aswell as potentially damage the shearing ram.6.3 Shearing gold ball bonds on gold metallization pads orsubstrates can lead to friction rewelding as illustrated in Fig. 4.As a strongly welded gold bond is sheared, the ball tends to tipaway from the ram and contact th
30、e substrate as it moves. Theball smears against the pad metallization and rewelds itselfoften several times before it finally clears the metallization.6.4 In bonding systems in which excessive intermetallicgrowth has formed around the ball bond, the shearing ram maycontact the intermetallic rather t
31、han the ball bond and thus the5Charles, Jr., H. K. and Clatterbaugh, G. V., “Ball Bond ShearingA Comple-ment to the Wire Bond Pull Test,” International Journal of Hybrid Microelectronics,Vol 6, No. 1, 1983, p. 171.6Harman, G. G. “The Microelectronic Ball-Bond Shear TestACritical Reviewand Comprehens
32、ive Guide to its Use, International Journal of HybridMicroelectronics, Vol 6, No. 1, 1983, p. 127; also Harman, G. G., Wire Bonding inMicroelectronics, Third Edition, McGraw Hill, 2010, pp. 110-118.NOTE 1Schematic diagrams of the ball shear test. (A) Horizontal sample and horizontal ram. (B) Horizon
33、tal sample and vertical ram.FIG. 2 Ball Shear Test ConfigurationsF1269 133shear readings can be in error (that is, weak ball bond shear ismasked by the shear strength of the strong intermetallic wreathsurrounding it.6.5 When the bond pad pitch becomes too small to practi-cally shear test (which appe
34、ars to be around 30 m pitch withcurrent equipment) then the only alternative is to use thedestructive bond pull test, Test Methods F459, and accept thatresultant value, even if the ball lifts or pulls up the bond pad,assuming that value is acceptable by pull test criteria.7. Apparatus7.1 Ball Bond S
35、hearing Machine Apparatus for measur-ing the ball bond shear strength are required with the followingcomponents:7.1.1 Shearing Ram Various shearing tools or rams havebeen recommended in the technical literature, but the ones thatappear the most effective have a flat chisel shape with ashearing edge
36、dimension equal to approximately 1 to 2-balldiameters as shown in Fig. 5. For 25.4-m (1-mil) diameterwire this dimension would be approximately 0.152 mm (6mils).7.1.2 Shearing and Gaging Mechanism Mechanism forapplying a measured vertical (or horizontal) force to theshearing is needed. The mechanism
37、 shall incorporate a meansfor recording maximum force applied and shall be capable ofapplying the shear force at a uniform rate of ram motion. Forceapplication rate can be variable (either continuously or in fixedsteps) to accommodate different shearing conditions andconfigurations, or both. In no c
38、ase should the ram speed exceed6.0 mm/s.NOTE 4It has been shown that the shear force is independent of forceapplication rate in the range from 0.25 to 6.0 mm/s.NOTE 5Electronic-strain gage-force reading mechanisms are theindustry standard; however, the dynamometer type mechanisms knownas“ gram gages
39、 may be used satisfactorily providing careful calibrationtest procedures are employed.7.1.2.1 The range of the force reading gage/sensor shall beselected so that the maximum scale reading will be no greaterthan three times the expected average ball bond shear strength.Anticipated force ranges for th
40、e various wire sizes and mate-rials covered by these test methods are summarized6in Fig. 6.NOTE 6The maximum scale range of the electronic strain gage withdigital readout may be larger than three times the expected average shearstrength providing the accuracy specified in 10.7.6 is maintained over t
41、heentire range of the load cell.7.1.3 Microscope and Light Source Zoom microscopewith a light source for viewing the device under test is needed.The minimum magnification shall be at least 60.7.1.4 Device Holder A clamping mechanism for rigidlyholding the device under test in either a horizontal or
42、verticalposition depending upon shear tester configuration is required(see 7.2).7.1.5 Calibration MassesAt least five masses (weights)with mass values known to an accuracy of 0.5 % (or better,such as NBS Class T or IOLM Class M2 (NBS Handbook105-1 and Circular 547. IOLM)3) sized to cover the shearin
43、gand gaging mechanism range of force measurements andsuitably configured so that they may be supported by the shearmechanism for calibration, are needed. In the case of horizontalshearing ram motion, the tester mechanism should rotate 90 toFIG. 3 Ball Shear InterferencesF1269 134allow the weights to
44、 be hung from the shearing ram. Otherindirect methods of calibration may also be possible for thisconfiguration.7.1.6 Shear Test TolerancesThe shear test sample holderor the shear test ram must be able to be positioned to tolerancesbetter than 610 m (6 0.4 mils) and the X and Y directions(plane of t
45、he bonding pad) and 5.0 m (60.2 mils) in the Z orthe above substrate direction. The shearing rams over travel(distance it proceeds from the point of ball contact) should belimited to 2-ball diameters. Additional over travel may beallowed in cases where the excessive ram motion does notdamage other b
46、onds or the device under test.7.2 Typical shear test configurations are illustrated in Fig. 7.View a shows a horizontal test system with horizontal shearingram motion. View b presents a vertical test system with verticalshearing ram motion.8. Sampling8.1 Since the shear test method is destructive, i
47、t shall beperformed on a sampling basis. The sample selected should berepresentative of the ball bonds of interest. The size of thesample and the method of selection shall be agreed upon by theparties to the test. The sample space should be as large aspractical (nominally 35 bonds) to ensure the pro
48、per statisticalinferences from quantities such as the mean shear force ( X)and its standard deviation ().9. Calibration9.1 Calibrate the ball bond shearing machine at the begin-ning and of each series of tests, or at the beginning and end ofeach day if the test sequence spans more than one day.9.2 F
49、or multifunction wire test machines, set up the testmachine in the proper configuration for the ball bond shear test,otherwise for a dedicated ball shear tester proceed with thecalibration steps in 9.3.9.3 Calibrate the shearing and gaging mechanism.9.3.1 For mechanisms or systems that incorporate a calibra-tion standard or mode, either calibrate the mechanism accord-ing to the manufacturers instructions or in accordance with theprocedure in 9.3.2.9.3.2 For non-electronic force mechanisms without abuilt-in calibration mode, select fi
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