Download as PDF, PPTX
![Real Data on Single Crystals
0.00 5.00 10.00 15.00 20.00 25.00
Strain 2 ε (%)
0.00
5.00
10.00
15.00
20.00
Stressσ/2(N/mm2)
[100]
m=0.5
Polycrystal
[111]
33
15/9/11](https://image.slidesharecdn.com/wgc1manufacturingseptember2011-130809213311-phpapp01/85/Basics-of-Bonding-Wire-Manufacturing-33-320.jpg)
Uploaded byChristopher Breach
Basics of Bonding Wire Manufacturing
The document discusses the processing and material properties of gold and copper wire, detailing the manufacturing processes, chemical analysis, microstructure, and mechanical properties. It highlights the effect of dopants on the wire properties, the principles of continuous casting, and various analytical techniques for assessing metal purity. Additionally, it covers the plastic deformation during wire drawing, the influence of grain structure on mechanical behavior, and the final wire properties obtained through annealing.
More Related Content
Similar to Basics of Bonding Wire Manufacturing
Basics of Bonding Wire Manufacturing
- 1. Gold and CopperWire Processing and Material Properties Dr Christopher Breach ProMat Consultants
- 2. Agenda ¤ Gold and CopperWire Processing and Material Properties ¤ Manufacturing Processes of Au, Cu and Pd-coated Cu Wires ¤ Wire Chemistry and Analysis ¤ Final Wire Properties 2 15/9/11
- 3.
- 4.
- 5.
- 6. Continuous Casting-Casting Machine Illustrationof a continuous casting machine chamber 6 15/9/11
- 7. Continuous Casting-Principle There isan uninterrupted liquid – solid interface There is a temperature gradient along and across the exit of the casting machine Solid metal must be extracted from the end of the die slowly enough so that the solid-liquid interface is not fractured 7 15/9/11
- 8.
- 9. Metal Purity Wire PurityClassifications ‘N’ % Metal Use Amount of Dopant (parts per million by weight) 5 99.999 Au: raw material for doping Cu: usable as a bonding wire NA 4 99.99 Doped bonding wire. 100 ppm limit 3 99.9 Micro-alloyed or alloyed bonding wire depending on composition. 2 99 Stiffer than other wires, slightly higher electrical resistivity. Thinner intermetallics compared to higher purity wires. 1% by weight limit for alloy elements including dopants (if any) 9 15/9/11
- 10. Dopants – GoldWire Element Atomic Radius (Å) Resistivity (µΩ-cm) Role Effect Ag 1.44 1.59 Dopant Be 1.13 4 Dopant Increase in yield and tensile strength Ca 1.97 3.43 Dopant Increase in yield and tensile strength Ce 1.82 73 Dopant Increase in stiffness La 1.88 57 Dopant Y 1.81 57 Dopant Pd 1.37 9.78 Dopant and alloy element In alloy wires helps reduce intermetallic thickness Pt 1.38 9.6 Dopant and alloy element 10 15/9/11
- 11. Dopants- Copper Wire ¤ Almost any metallic element added to copper causes it to get harder ¤ This is why 5N copper is often touted as easier to bond – it’s softer because it’s more pure ¤ Dopants are not normally added to copper wire ¤ Adding P has been considered because P is used in commercial copper ingots and rods as ¤ An oxygen getter ¤ To improve metal fluidity ¤ P also hardens copper 11 15/9/11
- 12. Doping How can partsper-million levels of dopants be controlled? Au (grams) Dopant (grams) +! Master alloy The master alloy is an alloy of known and controlled composition 12 15/9/11
- 13. Doping during Casting Addinggram amounts of master alloy to kg amounts of gold in the casting furnace allows accurate control of composition Au (kg) Master alloy (grams) + Au alloy with ppm dopant level 13 15/9/11
- 14. Chemical Analysis ofWire: ICP-OES 14 15/9/11
- 15. Chemical Analysis ofWire: ICP-MS 15 15/9/11
- 16. Sensitivity of ICP ¤ The resolution of ICP varies with the element Chart source: Evans Analytical Group! ICP-MS is more sensitive than ICP- OES i.e. detection limits are lower 16 15/9/11
- 17. ICP-OES vs. ICP-MS ICP-MShas detection limit (DL) capability in the parts per-trillion (ppt) range, ICP-OES has limited DL in the mid ppt range Source: Agilent’s ICP-MS primer brochure available online at http://www.chem.agilent.com/en-US/products/instruments/icp-ms Method Metals Approx. DL Range Advantages Disadvantages ICP-‐MS Most metals and non-‐ metals ppt Rapid and sensi=ve mul=-‐element method with wide dynamic range and good control of interferences Limited total dissolved solids (TDS) tolerance ICP-‐OES Most metals and some non-‐ metals mid ppb to mid ppm Rapid mul=-‐elemental method with high TDS tolerance Complex interferences and rela=vely poor sensi=vity GFAA Most metals but commonly Pb, Ni, Cd, Co, Cu, As, Se ppt Sensi=ve, few interferences Single element technique with limited dynamic range Hydride AA Hydride forming elements (As, Se, Tl, Pb, Bi, Sb, Te) ppt to ppb Sensi=ve, few interferences Single element, slow, complex Cold Vapour Mercury Hg ppt Sensi=ve, simple, few interferences Single element, slow, complex 17 15/9/11
- 18.
- 19.
- 20. Wire Drawing Multiple diesand multiple passes with liquid lubricant to reduce friction 20 15/9/11
- 21. Wire Microstructure ¤ Wiredrawing is a plastic deformation process ¤ Plastic deformation breaks large grains into small grains ¤ Smaller grains cause the material to become harder ¤ Breaking grains up also created defects that harden metals ¤ After drawing it is necessary to heat treat the metal to soften it ¤ The wire then undergoes final drawing and annealing 21 15/9/11
- 22. Plastic Deformation duringWire Drawing 22 15/9/11
- 23. Plastic Deformation ¤ PlasticDeformation occurs during wire manufacturing and bonding ¤ A very basic treatment is given here of plastic deformation of ¤ Single Crystals ¤ Polycrystals 23 15/9/11
- 24.
- 25. Wire Microstructure-Grains ¤ Eachgrain is a ‘single’ crystal ¤ E.g. Au wire 25 15/9/11
- 26. Crystal Structure ¤ Atomsare arranged within each grain with a specific geometry ¤ The geometry for Au and Cu is the same: Face Centred Cubic 26 15/9/11
- 27. Selected Properties ofPure Metals Element Neutral free atom diameter (Angstroms) Unit cell dimension a (Angstroms) Solid density (g/cm3) Resistivity (μΩ-cm) Melting point (°C) Au 1.44 4.079 19.3 2.05 1064 Cu 1.28 3.615 8.96 1.54 1084 Al 1.43 4.05 2.7 2.42 660 27 15/9/11
- 28. Crystal Planes &Directions ! <100> direction and (100) plane <101> direction and (101) plane <110> direction and (110) plane 28 15/9/11
- 29.
- 30. Anisotropy of ElasticProperties ¤ Solidity Index S S = 3G 4B Metal Elastic modulus in GPa, different crystal directions Bulk Modulus (GPa) Shear Modulus (GPa) G/B S <111> <110> <100> Au 115 85 42 171 27.4 0.16 0.12 Cu 75 72 63 138 48 0.35 0.26 Al 191 130 63 75.2 27.8 0.37 0.27 Ir ⎯ ⎯ ⎯ 371 209 0.56 0.42 30 15/9/11
- 31. Plastic Deformation Illustration ofa small single crystal under an applied shear force. Slip is expected in planar region indicated by the red box the simplest and smallest distance that gives rise to permanent deformation with a distance on the order of interatomic spacing. 31 15/9/11
- 32. Single Crystal UnderTension τR = F A cosφ cosλ = F A m Orientation of crystal affects strength 32 15/9/11
- 33. Real Data onSingle Crystals 0.00 5.00 10.00 15.00 20.00 25.00 Strain 2 ε (%) 0.00 5.00 10.00 15.00 20.00 Stressσ/2(N/mm2) [100] m=0.5 Polycrystal [111] 33 15/9/11
- 34. Single Crystals inTension 34 15/9/11
- 35. Orientation Change withStress Tension Compression 35 15/9/11
- 36. Single Slip ina Single Crystal Single crystal slip on a single slip plane in compression Plasticity of Micrometer-Scale Single Crystals in Compression. Michael D. Uchic,Paul A. Shade and Dennis M. Dimiduk. Annu. Rev. Mater. Res. 2009. 39:361–86 36 15/9/11
- 37. Dislocations-Defects that Make DeformationEasier 37 15/9/11
- 38. Dislocation Movement and MicroscopicPlastic Deformation 38 15/9/11
- 39.
- 40. Single Crystal MetalPurity and CRSS Metal Purity (%) Slip System Critical resolved shear stress τR C (MPa) Au 99.99 {111}<100> 0.9 Cu 99.999 {111}<100> 0.65 99.98 {111}<100> 0.94 Ag 99.999 {111}<100> 0.37 40 15/9/11
- 41.
- 42.
- 43. Polycrystal Deformation Behaviour Whensingle crystals are joined together as a polycrystal, contact modifies deformation Individual grains with different orientation can yield at different stresses For example, individual grains may be differently oriented 43 15/9/11
- 44. Polycrystal Deformation Behaviour Separated,each grain would deform like a single crystal CO-OPERATIVE deformation occurs due to contact Joined together, single crystal behaviour is changed⇓ 44 15/9/11
- 45. Ashby Model ¤ Ashbysuggested that polycrystal deformation can be broken into steps 1. M. F. Ashby. Phil. Mag. 21 (1970) 399. 1. Deform the individual grains (single crystals) so each yields at a stress given by its orientation 2. Put the grains back together 3. Where there are differences in deformation (strain) introduce grain boundary dislocations 45 15/9/11
- 46. Ashby Model Illustrated Deformgrains by dislocation movement in the grain Reassemble Remove overlap with creation of dislocations at the grain boundaries 46 15/9/11
- 47. Ashby Model Illustrated ReassembleRemove Overlap 47 15/9/11
- 48. Ashby Model Illustrated Dislocationsthat cause deformation within the grains are known as ʻ‘statistically stored dislocationsʼ’ (SSDs) Because they move through the grains but can be destroyed by meeting other dislocations or they can be randomly trapped force 48 15/9/11
- 49. Ashby Model Illustrated Thesetypes of dislocations are called ‘geometrically necessary dislocations’ Because they are necessary to maintain co-operative deformation between grains Creation of these types of dislocations at grain boundaries can strengthen metals 49 15/9/11
- 50. Plastic Deformation SSDsand GNDs disloca=ons created and moved inside grains all grains have different orienta=ons grain boundaries can block disloca=ons because neighbouring grains have different orienta=ons 50 15/9/11
- 51. Plastic Deformation SSDsand GNDs Trapping dislocations at grain boundaries requires more stress to generate more plastic deformation Movement of dislocations, creation of new dislocations and dislocation trapping results in higher strength 51 15/9/11
- 52. Dislocations and Strengthening ¤ Dislocations in some metals are created and destroyed at similar rates ¤ This results in weak strengthening with plastic deformation ¤ In other metals, creation outweighs destruction and dislocation density increases ¤ Tensile test curves of bonding wires can illustrate this effect 52 15/9/11
- 53. Weak and StrongHardening At constant strain rate !σ = Kεγ Constant Plastic stress Strain Strain hardening index 53 15/9/11
- 54. Strain Rate Hardening ¤ Dislocations are generated more rapidly in some materials by increasing strain rates. e.g. Cu wires !σ = C εm Plastic stress Constant Strain rate in s-1 Strain rate hardening index ! 54 15/9/11
- 55.
- 56.
- 57. Annealing and Recrystallization Before After Intermediate annealing Post annealing 57 15/9/11
- 58. Final wire annealingcurve Change in mechanical properties depends on furnace temperature as the illustration shows 58 15/9/11
- 59.
- 60. Final Wire Microstructure Cugenerally has a larger grain size due to more aggressive annealing Au grains : 300-1000nm Cu grains : 1000-3000nm Microstructure can vary across wires from the centre to the outside 60 15/9/11
- 61. Final Wire Orientation:Au vs. Cu Au and Cu usually have the same orientation after drawing More aggressive annealing of Cu wire changes the orientation from majority <111> to majority <100> <111> <100> 61 15/9/11
- 62. Variations in DrawnMicrostructure Variation of microstructure varies across wires changes mechanical properties G. A. Ber=, M. Mon=, M. Bietresato, L. D’Angelo. Proc. NUMIFORM ’07; Materials Processing and Design: Modelling, Simula=on and Applica=ons. American Ins=tute of Physics (2007). ∅275µm ∅210µm ∅175µm100µm 137.5µm 50µm 20µm 62 15/9/11
- 63. Elastic/Plastic Behaviour: SizeEffects The larger the grain size relative to sample diameter the more surface grains influence deformation Surface may grains deform like single crystals and inner grains like polycrystals G. Kim, J. Ni, M. Koç. J. Manuf. Sci. Eng. 129 (2007) 470. U. Engel, R. Eckstein. J. Mater. Process. Technol. 125 (2002) 2245. 63 15/9/11
- 64.
- 65. Mechanical Properties ofFinished Wire 4N Au : flat - small stress required to cause plastic strain T. Saraswa=, Ei Phyu Phyu Theint, D. Stephan, H. M. Goh, E. Pasamanero, D. R. M. Calpito, F. W. Wulff, C. D. Breach. ‘High Temperature Storage (HTS) Performance of Copper Ball Bonding Wires’. Proceedings of EPTC 2005 (Electronics Packaging and Technology Conference), Grand Copthorne Waterfront Hotel, Dec 7-‐9, Singapore 2005. 5N Au and Cu: steeper curves show that stress required to cause further elongation increases as the wire is further strained 65 15/9/11
- 66. Representative Wire Properties WireType Elastic Modulus (GPa) Yield Stress (MPa) Ultimate Tensile Stress (MPa) Cu wire A 88 172 254 Cu wire B 80 123 212 Cu wire C 96 136 238 Cu wire D 93 98 210 4N Gold 90 190 228 5N Gold 53 48 120 66 15/9/11
- 67. Work or StrainHardening Slope of the plastic region of the curve is often described by !σ = Kεγ Wire Yield strength (MPa) UTS (MPa) EL (%) Strain hardening index γ K (MPa) 5N Au 75 118 4.2 0.18 219 4N Au 190 228 4.4 0.06 281 Cu 175 250 12 0.15 380 Constant Plastic stress Strain Strain hardening index 67 15/9/11
- 68. Strain Rate Hardening Strainingmaterials at higher speeds can also cause hardening Higher speeds increase the rate at which dislocations are created in some materials and plastic stresses increase !σ = C εm Plastic stress Constant Strain rate in s-1 Strain rate hardening index 68 15/9/11
- 69. Strain-Rate Hardening Tensile testscan be used to measure strain rate sensitivity Strain rate hardening and sensitivity indices of Cu and Au bonding wires measured from tensile tests Wire Type Strain hardening index γ Strain rate sensi=vity m Cu wire 1 0.14 0.021 Cu wire 2 0.25 0.023 Cu wire 3 0.26 0.018 Cu wire 4 0.36 0.019 4N Au 0.06 0.006 The disadvantage of tensile tests is the small range of strain rates But the results give some idea of the different material behaviour 69 15/9/11
- 70. Strain and StrainRate Hardening Wires harden when deformed Strain Hardening Strain Rate Hardening ! 70 15/9/11
- 71. Copper Wire Purity& Strength N Srikanth, J. Premkumar, M. Sivakumar, Y. M. Wong, C. J. Vath III, 9th EPTC 2007, Singapore 71 15/9/11
- 72. Effects of CopperWire Purity Higher purity leads to larger grains Random orientation N Srikanth, J. Premkumar, M. Sivakumar, Y. M. Wong, C. J. Vath III, 9th EPTC 2007, Singapore 72 15/9/11
- 73.
- 74. Metal Coated BondingWires 74 15/9/11
- 75. Coated Wires: MetalCoated Cu Alternative is to plate Au or Pd on Cu Au Drill hole Insert Cu rod Draw Pd Drill hole Insert Cu rod Draw Coating uniformity can be a problem 75 15/9/11
- 76. Coated Wires: Aucoated Cu Spear shaped FABs due to difference in melting points Au (1064℃ melting) Cu (1083℃ melting) Only good for wedge bonding 76 15/9/11
- 77. Coated Wires: PdCoated Cu Uno et al, ECTC 2009 p1486 77 15/9/11
- 78. Metal Coated Wires Kaimoriet al, IEEE Trans Advanced Packaging 29 (2006) 227 78 15/9/11