Future Electronic Devices Technology in Cosmic Space and Electroless Ni/Pd/Au Plating for High Density Semiconductor Package Substrate

Transcription

1 JAXA 25 rd Microelectronics Workshop Future Electronic Devices Technology in Cosmic Space and Electroless Ni/Pd/Au Plating for High Density Semiconductor Package Substrate November 2, 2012 Yoshinori Ejiri Tsukuba Research Laboratory

2 Contents 1. High-speed Ball Shear Test 2. The Influence of the Ni Thickness on the Joint Reliability (SJR) 3. The Intermetallic Compound (IMC) Growth at Ni/Pb-free (Sn-3.0Ag-0.5) Interface 4. E less /Pd/Au Plating for High Density Semiconductor Package Substrates

3 Structure of BGA Assembly 2 Gold Wire Semiconductor Chip Die Bonding Material Wire Bonding Joint Package Substrate Printed Circuit Board Molding Material Ball

4 Wire Bonding 3 Copper Line Aluminum Electrode LSI Gold Wire Resist Die Bonding Material Package Substrate Gold Plated Terminal

5 Ball Joint 4 Copper Pad Package Substrate Resist Ball Ball Gold Plated Terminal

6 Characterization of Gold Plating 5 Item Wire Bondability OK OK Wire Bondability after Aging* Wire Bondability after Aging* and Plasma** E lytic Ni/Au (5/0.5 µm) OK OK E less /Au (ENIGEG) (5/0.5 µm) NG OK Joint Reliability OK NG E less /Pd/Au (ENEPIGEG) (5/0.1/0.3 µm) OK OK OK OK * Aging : 150 ºC, 50 h ** Plasma : O 2 plasma

7 Electrolytic vs. Electroless Plating E lytic Ni/Au 6 E less /(Pd)/Au Plating stub is is necessary for metal finish. Obstruction of High Density & High frequency Plating stub is is not necessary. High Density & High Frequency

8 Issue of the E less Plating 7 : 5 µm (Present) Bridging Nickel 20 µm Copper Line High Density Thin E less Film

9 Contents 1. High-speed Ball Shear Test 2. The Influence of the Ni Thickness on the SJR 3. The IMC Growth at Ni/ 4. E less /Pd/Au Plating for High Density Semiconductor Package Substrates

10 High-speed Ball Shear Test 9 Shear Speed 0.5, 20, 200, 1000 mm s High -1 Speed 10 mm Low High s -1-1 or more (JEDEC JESD22-B117A) Shear Tool Ball Ductile Brittle Mask Copper Pad Package Substrate

11 Ductile Low Speed (0.5 mm s -1 ) Shear Force (N) Displacement (µm) Strength Shear Tool Shear Strength <Interface Ductile 500 µm Interfacial Strength 10

12 Shear Force (N) Brittle High Speed (200 mm s -1 ) Displacement (µm) Interfacial Strength Shear Tool Brittle 11 Shear Strength Interface < 500 µm Strength

13 Ductile Fracture Rate / % High-speed Ball Shear Test Low Speed /Au Shear Speed/ mm s -1 / P/Pd/Au 12 Ductile Brittle : 5 µm Pd : 0.1 µm Au : 0.3 µm

14 E less Surface after Au or Pd Dissolution 13 Au /Au Removal /Pd/Au Au Removal Pd 3 µm Corrosion at Boundary No Corrosion 3 µm

15 Contents 1. High-speed Ball Shear Test 2. The Influence of the Ni Thickness on the SJR 3. The IMC Growth at Ni/ 4. E less /Pd/Au Plating for High Density Semiconductor Package Substrates

16 E lytic vs. E less Plating 15 E lytic Ni E less Ductile Fracture Rate / % Ductile Fracture Rate / % Reflow Cycles Shear Speed : 200 mm s -1 Excellent Thickness of Ni and / µm Ductile Excellent Brittle

17 Influence of Reflow Cycles on IMC Growth Reflow Cycles 1 cycle 3 cycles 7 cycles 16 E lytic Ni E less Ni Thickness of Ni and : 1 µm E less Excellent Ni 3 µm 3 µm

18 Contents 1. High-speed Ball Shear Test 2. The Influence of the Ni Thickness on the SJR 3. The IMC Growth at Ni/ 4. E less /Pd/Au Plating for High Density Semiconductor Package Substrates

19 E lytic vs. E less Plating 18 E lytic Ni E less Ductile Fracture Rate / % Ductile Fracture Rate / % Reflow Cycles Shear Speed : 200 mm s -1 Excellent Thickness of Ni and / µm Ductile Excellent Fracture modes are different at <1 µm Brittle

20 Influence of Thickness on IMC Growth : 0 µm : 0.1 µm 19 : 0.3 µm : 1 µm Reflow Cycles : 7 cycles 5 µm

21 IMC Growth ( = 0 µm) 20 6 Sn 5 1 cycle 3 cycles 3 µm Crack Crack 7 cycles 6 Sn 5 Cracks 6 Sn 5 Poor Reliability

22 IMC Growth ( = 0.1 µm) 21 (, Ni, Pd) 6 Sn 5 Sn//Ni 3 µm 1 cycle 3 cycles (, Ni, Pd) 6 Sn 5 Sn//Ni 7 cycles Uniform IMC Excellent Reliability

23 IMC Growth ( = 0.3 µm) (, Ni, Pd) 6 Sn µm Sn//Ni 1 cycle 3 cycles (, Ni, Pd) 6 Sn 5 7 cycles Two Kinds of IMC Structure Sn//Ni Poor Reliability

24 FIB/SIM Observation Results of IMC Microstructure ( = 0.3 µm) 23 I II 1 µm (, Ni, Pd) 6 Sn 5 1 µm Voids I II 2 µm Reflow Cycles: 3 cycles Sn//Ni

25 TEM-EDX Analytical Result Sn 24 (, Ni, Pd) 6 Sn 5 Sn//Ni Ni 1 µm : 0.3 µm, Reflow Cycles: 3 cycles

26 Generation Model of Voids 25 1 µm Cross-sectional Structure 3 µm IMC Voids 10 µm Surface Morphology Kirkendall Voids Boundary Diffusion

27 Diffusion Models Surface Diffusion 26 Subgrain Boundary Pipe Diffusion Lattice Diffusion Boundary Diffusion Dislocation

28 IMC Growth ( = 1 µm) 27 (, Ni, Pd) 6 Sn 5 1 cycle 3 cycles 3 µm 7 cycles Uniform IMC (, Ni, Pd) 6 Sn 5 Excellent Reliability

29 Contents 1. High-speed Ball Shear Test 2. The Influence of the Ni Thickness on the SJR 3. The IMC Growth at Ni/ 4. E less /Pd/Au Plating for High Density Semiconductor Package Substrates

30 E less /Pd/Au Plating for High Density Line-Space 29 Resin Wiring Space: 10 µm Wiring Height: 7 µm 6µm : 2 µm, Pd: 0.1 µm, Au: 0.3 µm Wire Bonding Reliability Joint Reliability Excellent

31 Summary 30 (1)The minimum thickness of electroless /Pd/Au for the good solder joint reliability is 1 µm. In the case of electrolytic Ni/Au, the minimum Ni thickness is 3 µm. (2) The growth of the IMC during the reflow cycle and the solder ball joint reliability changed widely with the thickness of the electroless (0 to 1 µm). (3) When the thickness of electroless was 0.3 µm, the adhesion at / interface and the solder ball joint reliability after reflow cycles was poor. The reason was thought that Kirkendall voids were generated at the interface by the copper diffusing to the IMC passing through the boundaries of electroless.

32 Thank you!

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