Solder in the Age of 3D Semiconductor Assembly - SMTA
Solder in the Age of 3D Semiconductor Assembly - SMTA
Solder in the Age of 3D Semiconductor Assembly - SMTA
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Copyright © 2011 Indium Corporation<br />
Indium Corporation<br />
<strong>Solder</strong> and Flux <strong>in</strong> <strong>the</strong> <strong>Age</strong> <strong>of</strong> <strong>3D</strong><br />
Interconnects<br />
Dr Andy C Mackie<br />
Global Product Manager
Copyright © 2011 Indium Corporation<br />
Packag<strong>in</strong>g Challenges <strong>in</strong> <strong>the</strong> 2010’s<br />
• Wafers th<strong>in</strong>ned<br />
– Dom<strong>in</strong>ant by 2016<br />
• Memory:
ITRS 2010<br />
Copyright © 2011 Indium Corporation
Copyright © 2011 Indium Corporation<br />
TechSearch International Data (2010)<br />
Copper Pillar<br />
4100k<br />
300mm<br />
eq
Flip-Chip Flux<br />
Evolution 2010-2015<br />
Bus<strong>in</strong>ess Confidential © 2011 Indium Corporation
Bus<strong>in</strong>ess Confidential © 2011 Indium Corporation<br />
Standard Waferbump<strong>in</strong>g Processes<br />
<strong>Solder</strong><br />
bumps and<br />
copper pillar<br />
microbumps<br />
<strong>Solder</strong><br />
bumps only
Copyright © 2011 Indium Corporation<br />
Plated Bumps<br />
Just after photoresist strip<br />
Pb90Sn10<br />
SnAg<br />
Source: Scheele, D. “Resist Removal Solutions <strong>in</strong> Advanced Packag<strong>in</strong>g<br />
Applications” IWLPC, Oct 2009
Copyright © 2011 Indium Corporation<br />
Plated Bumps<br />
After Waferbump<strong>in</strong>g Flux Reflow and Clean
Copyright © 2011 Indium Corporation<br />
Oxidation and Formic Acid Reactions<br />
O 2<br />
Sn(IV) O 2<br />
Sn(II) O<br />
SnO 2 + 2HCO2H -> Sn + CO2 +H2O<br />
SnO + HCO2H -> CO2 +H2O<br />
Sn / Ag<br />
Sn+ ½ O2 -> SnO + ½ O2 -> SNO2
Copyright © 2011 Indium Corporation<br />
Fluxless and Fluxed Reactions<br />
• Fluxless:<br />
– Reduction process:<br />
– Gas phase<br />
• Adsorption <strong>of</strong> molecule on oxide<br />
• Reaction<br />
• Desorption <strong>of</strong> products<br />
• Fluxed:<br />
– Reaction process:<br />
– Liquid phase<br />
• Reaction<br />
• Dissolution
Copyright © 2011 Indium Corporation<br />
Fluxless Vacuum Reflow<br />
Spatter and Golfballs<br />
<strong>Solder</strong> paste:<br />
Consistent problem<br />
Plat<strong>in</strong>g: Issues if<br />
organic chelates<br />
not removed<br />
Vacuum<br />
and reflow<br />
SnO2 preferred over<br />
SnO on high energy<br />
surfaces:<br />
• Edges<br />
• Rough surfaces<br />
Vacuum<br />
and reflow
Bus<strong>in</strong>ess Confidential © 2011 Indium Corporation<br />
Flip-Chip / WLCSP Attach Processes
D2D Thermocompression Bond<strong>in</strong>g<br />
Copyright © 2011 Indium Corporation
Copyright © 2011 Indium Corporation<br />
Dipp<strong>in</strong>g No-Clean Flip-Chip Fluxes<br />
Adhesion (Shear) Strength<br />
Underfill 1 Underfill 2 Underfill 3 Underfill 4
Copyright © 2011 Indium Corporation<br />
Copper Pillar Flip-chip Flux<br />
WS641<br />
• Flux application<br />
method:<br />
– Dipp<strong>in</strong>g<br />
• Reflow:<br />
– Thermocompression<br />
bond<strong>in</strong>g
Copyright © 2011 Indium Corporation<br />
Copper Pillar Flip-Chip: Chip-on-Chip<br />
Jo<strong>in</strong>t Quality: WS641<br />
• X-ray Inspection<br />
• No jo<strong>in</strong>t defect was found for WS641<br />
(641-96-7)
Copyright © 2011 Indium Corporation<br />
Copper Pillar Flip-Chip: Chip-on-Chip<br />
Cleanability: WS641<br />
Excellent cleanability<br />
(Passed customer test<strong>in</strong>g)<br />
Top Die: SiN<br />
Bottom Die: PI<br />
resist (dry film)
Interposer to Substrate<br />
Challenges from Prior Reflow<br />
Copyright © 2011 Indium Corporation
Thank you!<br />
Copyright © 2011 Indium Corporation
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