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Micro mechatronics 1part 7: bonding
HalbleiterkontaktierungDie- and wirebonding
Prof. Fritz J. NeffDirector of the Laboratory for Micro mechatronics and Hybrid integrated thick film circuitSat the University of AppliedSciences Karlsruhe (FH), 16. August 2004
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 2
Definition BondingBonding is the electrical or mechanical connectionbetween the pads of a semiconductor and those of the substrateDie bonding is the mechanical connection betweena semiconductor with the substrateWire bonding is the electrical connection betweenthe semiconductor and the substrateFlip-chip-bonding is the only bonding technology which allows same time in one step to realize themechanical and the electrical connection between a semiconductor and the substrate
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 3
Use of bare dies
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 4
Parameter: thick film metalisation
AgPd- and AgPt-films are fit forbonding withAl-wire with d > 150 µm
Au-films are fit for bonding withAlSi1- and Au-wire d < 50 µm
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 5
Parameter: surface profile
Influences of the pad surface to the bond:
- peak-to-valley-hight,- adhesion of printed film/layer,- thickness of metallisation,- homogenity of layer,- impurities in the layer (killing particles!),- components of the paste like organic binder,
yield of metall and frit
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 6
Parameter: composition of printed film
Less organic binder means higher yield of metal and therefor low values of peak-to-valley-hight
Repeating of the fireing process will cause better surface
Very thin film contain less organic binderand therefor better surface.
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 7
Parameter: intermetallic connections
Homogenious connections will not cause anyproblemsHeterogenious connections are causing migrationof particles and therefor the formation of intermetallic connections.
Aluminium - Wedge - Bond
AuAl2
Au - Schicht
Substrat
Au Al5 2
Kirkendall - Voids
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 8
Parameter: intermetallic connections
thermal and mechanical stability over long time of use only is possible by homogenious connections[Au/Au oder Al/Al]but:most used Au/Cu- or Au/Al-connections and
therefor the result areintermetallic connection,
problems are causing the Kirkendall-Voids; holeswhich are formating because of different diffusionconstants of the different materials
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 9
Diebonding with glueing
most used technology to connect the rear side of the die/chip with the prepared diepad on thesubstrate; the advantage is also to compensaterelative elongations between the different materials with help of the elasticity of the glue.
Elektrisch leitenderZwei-Komponenten-Klebstoff
Die
BondpadDiepadKeramiksubstrat
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 10
Diebonding
Die bonder inLaminar flow box
class100
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 11
Die BondingLow pressuregripperoverhead thesubstrate
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 12
Pad surfaces
aluminiumgold copper
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 13
Wire bonds
Ball-wedge-bonding (left)with Au-wire
Wedge-wedge-bonding (rigth)with Au- or Al-wire
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 14
Wire bonding
Thermo compression bonding, TC(Temperature T and bond force N) withAu-Draht
Thermo sonic bonding, TS (Temperature T,bond force N and ultra sonic US)with Au- (Cu-, Pd-) wire
Ultra sonic bonding, US (Ultra sonic US and bond force N) with Al- (Au-) wire
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 15
Micro-friction solderingby ultra sonic power
one of the two friction partners have to have a higher plasticity (wire)
the surfaces of the partners should not becontaminated or oxidated
the force/energy of friction soldering is higherthan the linkage force and therefor result an approach of the two different lattice and so several new local connections
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 16
Ball-wedge-bonding
Thermosonic bondingfor only gold wires
diameters 25 µm - 32 µm
Capillary tubeGold wire
Wire grip
Wedge-bonding point
Ball-bonding point
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 17
Ballbond and tool
thermal energyand
nominal forceand
ultra sonic energyresult in
friction and plasticflow of the wire
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 18
Ball-Wedge-BondingBond parameters for dAu = 25 µm
Substrate temperature: ≤ 150°Cnominal force: 300....1000mNultra sonic energy: 0,1......1Wsoldering time: 40.......60ms
each new combination of materials and tools will cause new parameter values!
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 19
Ball-Wedge-Bonding sequence
El. dischargeto form the ball
Loop forming
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 20
Ideal Ball-Wedge-Bonds
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 21
Ball-wedge-bonding
Ball-wedge-bonderin LMHS
in theLaminar Flow Box
class 100
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 22
Wafer Bumping= FCB-preparation
tchnologies forwafer bumpingPrinting of solderby- stencil or- stamp printingBall bumping by- ball bonder
LM 324
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 23
Ball-Wedge-Bonding
ball bondson LM324
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 24
Wedge-Wedge-Bonding
Ultra sonic bondingfor AlSi1-wires;diameters 25µm - 32µm
Wedge-tool Wire grip
Al-wire
First wedge bond
Scond wedge bond
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 25
Wedge-bonding tool
nominal force andultra sonic energy result in friction and plastic flow of the wire material
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 26
Bond tools and materials
For Al-wires, tools made of tungsten carbideFor gold wires, tools made of titanium carbide orosmide.
30°
60°
45°
a.) b.) c.)
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 27
Wedge-Wedge-BondingBond parameters for dAlSi1 = 25µm
Substrate temperature: ~ 20°Cnominal force: 25 ...40 cNultra sonic energy: 0,5 ...1 Wsoldering time: 30....50 ms
each new combination of materialsand tools will cause new parametervalues!
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 28
sequence of wedge-wedge-bonding
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 29
perfect wedge-wedge-bonds
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 30
Wedge-Wedge-Bonding
Wedge-Wedge-Bonderin LMHS
inLaminar Flow Box
class 100
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 31
Wedge-bond on die bond-pad
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 32
Materials for wires
goldaluminiumpalladium
copper
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 33
Physikal properties of wire materialsPhys. properties Dimension Au
99,99Cu Pd Al 99,99 AlMg0,5 AlSi1
Melting point °C 1063 1083 1554 660 650 -659
655 -660
Elasticity module kN/mm² 78 126 121 71 69 66
Shearing module kN/mm² 28 38 50 27 27 27
therm. conductivity at 20°C
W/mK 312 390 75 230 198 195
therm. Expansion coefficient
10-6K-1 15,3 17,6 11,5 25,3 25,1 25
El. resistance Ωmm²/m 0,022 0,017
0,099
0,029 0,03 0,03
therm. resistancecoefficient
10-3K-1 3,72 4,07 3,97 4,14 3,98 3,95
Length resistance at 25µm and 20°C
Ω/m 44,8 34,6 201,7
57,073 61,2 61,15
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 34
Gold wires
used for bei- US-Ball-Bonding,- US-Ball-Bumping,- TS-Wedge-Wedge-Bondingwire diameters7,5µm < d < 100µm, Standard 25µm and 32µm
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 35
Gold wiresrequirements:- minimale hardness and hardness
increase- free of oxide- chemical inerteimportant features:- max tension force- max elongationcomponents of the alloy:- Y, Fe, Cu, Ag,...with < (0,01-0,02)%
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 36
Gold wires
Important is therecristallisation
important therefor theused alloy- increase of tension- increase of elongation.
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 37
Aluminium wiresused for- US-wedge-wedge-bonding,wire diameters- thin wires 7,5µm < d < 100µm,
alloy of AlSi1 or AlMg0,5Standard 25µm and 32µm
- thick wires 100µm < d < 500µm (pure Al)
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 38
Aluminium wiresrequirements:- minimale hardness and hardness
increase- free of oxide- chemical inerteimportant features:- tension- elongationcomponents of the alloy:- Si, Mg
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 39
Aluminium wiresAlSi1 Al
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 40
Length of bonding wire
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 41
Problems with increaseof packing density
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 42
Resistance of Bonding wires
d = diameter of wireσ = el. resistancelges = length
[ ]Ω∗
=d
lR gesges σ1
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 43
Induktivity of bonding wires
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 44
Induktivitybetweenparallelbondingwires
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 45
Flip-Chip-Bonding
4 circuits on same 2“ x 2“ –Al2O3-Substrate,LM 324 is prepared with Au-ball-bumpsfor flip-chip-bonding.
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 46
Au-Ball-Bumping
1. Au-ball- as result of el. discharge2. Au-ball-bumping steps
1
2
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 47
Au-Ball-forms
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 48
•Printing of Ni/Au Bumps on the wafer(UBM Under Bump Metalisation)
•Printing of solder paste
•Melting of solder paste (Reflow)
•Washing of the wafer
Wafer Bumbing (Pac Tech)
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 49
Flip Chip Bonding with LM324 amplifier
• dimensions: 65 Mil x 62 Mil, ca. 1625 µm * 1550 µm • max. temperature: 150°C
• thickness of chip/die: 15 Mil
• Bonding Pads : 4 x 4 Mil
• Tolerance : ± 10%
1 Mil = 25 µm
Important values
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 50
LM324 without and with Au-Bumps
Prof. Fritz J. Neff, Steinbeis TZ Mechatronik-Karlsruhe 51
Flip-Chip-Bonding
die positioningwith help of image treatment by 2 cameras