Introduction of IMS Technology for Advanced Solder Bumping on Wafers / Laminates Science & Technology IBM Research Tokyo Yasumitsu Orii, PhD Senju Metal Industry Co.,TW Deputy General Manager Lewis Huang
What is IMS (Injection Molded Solder) technology? C4NP (C4 New Process) for wafer bumping - in volume production in IBM since 2007 Mold fill Solder Transfer Wafer Glass mold Mold fill + Transfer -> One Process Molten Solder IMS head Mask (resist) Wafer or laminate Metal pad Very simple process Green process No flux, No formic acid Minimum solder waste Pure solder injection Higher solder volume Extendible to very fine pitch Solder alloy flexibility One pass for multiple solder sizes Injection of molten pure solder into through holes in N 2 environment molten solder wets on metal pads (or metal pillars) w/o flux. formation of IMCs (intermetallic compounds) at solder/pad interface. solidify solders in N 2 environment.
IMS (Injection Molded Solder) technologies Reusable Mask IMS for laminate bumping - ideal for high volume solder - available to skip solder bumping on chip side. Kapton mask Solder Laminate Remove mask Mask-less IMS for laminate bumping - ideal for low cost & fine pitch application As received laminate Solder IMS with Resist Mask for wafer/laminate bumping - Direct solder deposition on wafers/laminates without transfer Resist mask Solder Laminate Strip resist mask Resist mask Cu or Ni UBM IMS & strip resist mask & Etching seed layers C4 bump Wafer Resist mask Cu pillar Solder Capped Cu pillar bump
Cons. Pros. Technology IMS (Injection Molded Solder) technologies Reusable mask IMS Mask-less IMS IMS with resist mask laminate laminate Wafer or laminate No voids in solders Easy control of alloy composition Can make very high volume solder on laminates & wafers Good for island type I/O pads such as laminates No voids in solders Easy control of alloy composition No limitation in a size No limitation in pitch Very low cost No mask & no alignment No cost increase in finer pitch No voids in solders Easy control of alloy composition Can make very high volume solder on laminates & wafers Can be applied to finer pitch below 100 um pitch Can be applied to panel size laminates and wafers Tooling investment is required Difficulty of high volume production Currently, only singulated laminate or wafer is possible. Tooling investment is required Lower solder volume Tooling investment is required Photolithography is required Need some evaluation or development for the resist materials and process on high volume production
Target area (Possibility of IMS technology) IMS has a wide capability of the solder bumping compared with the commercially available bumping technologies; - from wider pitch (big bump) to finer pitch (small bump) applications - flexibility of solder alloy from pure Sn to ternary with minor alloy doping
20 60 μm Wafer IMS technology solder bumping on wafers SAC 305 1μm Cu 2μm Ni 20μm Cu
Wafer IMS results on different Cu thickness 40μm thick Cu pillar 2μm thick Cu UBM Dry film (60μm) Cu pillar Dry film Cu UBM As received After IMS Dry film SAC 305 Dry film SAC 305 After stripping dry film Particular geometry achieved is unique in industry. Straight sidewalls w/ round top of the solder bump on pillar No need additional reflow. It should help with fine pitch. Molten solder injection w/o flux No voids in solders. Ability to control solder composition readily. No change in throughput even though solder volume increased.
Wafer IMS bumping results on 8 inch wafer Demonstrated Wafer IMS bumping with 8 inch wafer Wafer IMS demonstration with various opening size in 8 inch wafer!!! Opening size Shape : 50μm ~ 200μm : Circle & Square 100μm, 250μm pitch 50μm, 200μm pitch 75μm, 225μm pitch 75μm, 125μm pitch 75μm, 175μm pitch 75μm, 150μm pitch 200μm, 400μm pitch 150μm, 300μm pitch 175μm, 350μm pitch 50μm 50μm solder bump 50μm diameter solder bump 75μm diameter
Concerns Advantages Technology Wafer bumping technologies Micro-ball mounting Electroplating Wafer IMS HVM tooling is in market bumping down to 60um dia. balls. Enough knowledge for processes, qualification, and cost. Ability to control solder composition readily. No voids in solders. Question of manufacturing tool availability for bumping 25um dia. balls. Tooling development could be required for fine pitch. Cost increase for making and handling small size balls. No way to use different I/Os size. HVM tooling is in market. Enough knowledge for processes, qualification, and cost. Easy to achieve fine pitch. Only pure Sn or binary solder composition. Solder composition uniformity. Possible voids in plated solders. Additional reflow after solder plating. Cost difference in Cu plating vs. solder plating. Cost for plating solutions and handling chemical waste of plating solutions. Ability to control solder composition readily. Not limited to binary composition. Bump height uniformity, even for different I/Os size and shape and Cu pillars have non-uniformity. No need of flux. No voids in solders. Green process / Minimum waste Head change : solder alloys change. If company does not have solder plating tools, easy to start IMS with low cost. Process & material optimization required. (prototype tool : ready, material : under development) HVM tooling optimization.
Laminate IMS Technology solder bumping on organic laminates Organic Laminate Cu pad ~ 63 μm Solder mask
Laminate IMS technologies Reusable film mask wide Organic laminate (a) Alignment mask N 2 Reusable Mask Mask-less (a) As received laminate Organic laminate Solder resist (SR) N 2 IMS with resist mask Organic laminate (a) Opened SR (b) Apply resist mask (b) Molten solder injection (b) IMS (c) Opening resist mask (lithography) Solder (c) Solidification of solder (c) Solidify solder (d) IMS in nitrogen (d) Mask separation (e) Strip resist mask (d) Reflow w/ flux (f) Reflow (optional)
Laminate IMS technologies A: Mask IMS (132μm pitch) Mask IMS bump height over solder resist H A F C E *Mask IMS 53.3μm over SR. D B IMS bump height distribution tighter then with paste printing G I B: Mask-less IMS (132μm pitch) Solder height above solder Average Std 17.9 mm 1.8 Solder volume and bump height are depended on solder resist opening design. No residue on solder resist ~ ideal for low cost (very fine pitch) ~
Summary IMS technology was demonstrated with organic substrates and wafers on different Cu thickness (Capable for solder capped Cu pillar structure) with 8 inch size wafers with 13μm diameter and 50μm height bumps with TSV (Through Silicon Via) IMS is an attractive technology, and IMS has many possibilities as well as solder bumping! TSV filling Bumping on Si / Organic / Glass IP Pre-soldering on C4 pads Laminate via filling BGA ball bumping
Introduction of IMS technology for advanced solder bumping on wafers / laminates Equipment Portion Contents IMS Tools & Process (Structure) Micro Bump Status (Under 50um) Cross Section, IMC & Bump Height (Coplanarity) Senju Metal Industry Co.,ltd 2013 Senju Metal Industry Co., Ltd. All rights reserved.
IMS Tools(Laboratory tool) <Work size> IMS-50: 50mm IMS-200: 8 inch wafer IMS-300: 12 inch wafer IMS-50 IMS-200 Developed year: 2011 2013 IMS-300 2014 (Evaluating now) IMS process N2 pressure Melting solder Mask SR DFR wafers / Laminates 15
Tool structure IMS Head 4 th Stage Cooling 3 rd Stage IMS Cooling plate Index table Heating plate Touch panel operation Carrier 1 st Stage Loader / Unloader Heating plate 2 nd Stage Pre-heater Condition~ Solder : SAC305 3 rd stage : 250 Solder temp : 250 Head pressure : 0.3MPa Solder pressure : 0.06MPa Head speed : 2mm/s Resist thickness: 20um
Micro bump status (Under Φ50um) 8 inch wafer Condition~ Solder : SAC305 3 rd stage : 250 Solder temp : 250 Head pressure : 0.3MPa Solder pressure : 0.06MPa Head speed : 2mm/s Resist thickness: 20um Pad Diameter Φ50um Φ40um Φ30um Φ20um Pitch 100um 80um 60um 40um 500 1500 17
Pad Diamete r Φ50um Φ40um Φ30um Φ20um Pitch 100um 80um 60um 40um Cross section 1500 1700 2000 3000 IMC 18
Bump height (um) Resist: 20um Bump height 14 12 10 8 6 4 2 0 Φ50umK Φ40umK Φ30umK Φ20umK Resist opening size Solder: SAC305 Solder temp: 250 Plate temp: 250 Solder pressure: 0.06MPa Head speed: 2mm/sec Resist thickness: 20um Resist opening size Wafer Measured value (N=20) Unit: um Ave. SD Φ50 10.7 11.2 11.3 11.5 12.3 12.0 11.5 10.9 11.9 11.6 11.2 11.0 11.1 10.9 11.8 12.0 12.0 12.0 11.5 11.2 11.48 0.459 Φ40 10.7 11.4 10.1 10.2 11.5 11.6 11.4 11.1 11.7 12.0 10.5 10.7 10.4 11.4 11.8 11.5 10.7 10.3 10.3 10.5 10.98 0.609 Φ30 8.2 8.0 8.3 7.9 9.8 8.1 8.0 9.4 9.0 8.1 9.2 8.6 9.5 8.5 9.3 8.0 9.5 9.1 9.3 9.0 8.73 0.631 Φ20 5.4 5.3 4.5 4.3 4.6 5.2 4.8 5.3 5.2 5.3 5.3 4.4 4.8 4.3 4.7 4.9 4.5 4.5 4.4 5.6 4.86 0.411
Laboratory & Evaluation ~Technical support~ IMS Demonstration Sample Preparation Evaluation & Inspection IMS-50 IMS-200 Clean room: Class 1000 (0.5um) If you are interested in IMS technology, please contact us! <Representative person> Lewis Huang / 黃智堯 Email: lewis@senju.com.tw Laboratory location:senju Metal Industry Co.,Ltd HQ 23 Senju Hashido-Cho Adachi-ku Tokyo, Japan 120-8555 <Contact person> Takashi Nauchi Email: tnauchi@senju.com
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