Underfilling Flip Chips on Hard Disk Drive Preamp Flex Circuits and SIPs on Substrates using Jetting Technology

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Underfilling Flip Chips on Hard Disk Drive Preamp Flex Circuits and SIPs on Substrates using Jetting Technology Michael Peterson Director, Advanced Engineering Belton mjpeterson@integraonline.

1 Underfilling Flip Chips on Hard Disk Drive Preamp Flex Circuits and SIPs on Substrates using Jetting Technology Michael Peterson Director, Advanced Engineering Belton Steven J. Adamson Market Manager Asymtek Agenda Package Classification Underfill Examples HDD PCB & Flex SIP Why underfill components? Reliability data Jetting Overview Dispensing Technology Comparison Jet Theory of Operation Example of how jet dispensing can save time and space when underfilling Summary 1

Encapsulation Methods to Protect Delicate

2 Encapsulation Methods to Protect Delicate Electrical Connections Underfill Dam & Fill Glob Top Package Classification 35 mm Old style Ball Grid Array (BGA) Chip Scale Package (CSP), Micro BGA Flip Chip (FC) 1.2 x chip size Interposer 760 micron balls 300 micron balls 75 micron balls (may be redistributed I/O) 2

Underfill Examples CF Hard Disk Drive BGA Underfill Compact Flash Connector Flip Chip Underfill Note: Sample parts from a build analysis report Parts

Height Solder Balls Distance to Neutral Point (DNP) Silicon Die System PCB Crossection of an Array Package CTE Values Silicon 3 ppm / deg K Solder 21

3 Underfill Examples CF Hard Disk Drive BGA Underfill Compact Flash Connector Flip Chip Underfill Note: Sample parts from a build analysis report Parts shown for illustration only Why Underfill? Height Solder Balls Distance to Neutral Point (DNP) Silicon Die System PCB Crossection of an Array Package CTE Values Silicon 3 ppm / deg K Solder 21 ppm / deg K PCB 17 ppm / deg K Polyimide 16 ppm /deg K Sheer DNP ((CTE Carrier X Τ Carrier ) (CTE Si X Τ Si )) Strain = with no underfill Height Flip Chip Chip Scale Package 10mm / 0.075mm = mm / 0.250mm = 40 DNP Ball Height CSP approx 3x less stress 3

resultant effect on the solder connection CSP Underfill protects portable equipment from Shock and

4 Why Underfill CSP s? How the Board and Device Move Relative to Each Other Displacement, board-die Z-axis and the resultant effect on the solder connection CSP Underfill protects portable equipment from Shock and Vibration In general RoHS (No Lead) I/O potentially susceptible to impact damage I/O Solder Bump Failure Solder Bump PCB Trace Open Circuit / Intermittent failure Crack Initiation 4

5 Why Underfill? Comparison of Thermal Cycle Results on Flip Chip F. Nakano, T. Soga, S. Amagi, Resin - Insertion Effect on Thermal Cycle Resitivity of Flip Chip Mounted LSI Devices, ISHM 1987 proceedings, pp Drop Test Comparison Results R. Wayne Johnson, Yueli Liu, Guoyun Tian, Shyam Gale, Pradeep Lall Auburn University On board 5

6 What Tools are Available to Dispense Underfills Time / Pressure Auger Displacement Jet X Not consistent Slow Fast but uses a needle Very Fast No needle Common Needle Problems No bent needles No chipped die No dripping positive shut-off Reduced part interference Dispense height variations Fluid left on needle Needle path is not always square at corners and it can damage the die 6

Jet vs. Needle Tight Packaging / Tight Keep-outs CL 28 gauge needle OD - 0.4mm ID 0.2mm 0.1mm jet nozzle 0.1mm stream CHIP CAP CHIP CAP 0.7mm (0.028 ) 0.4 wide fluid line Leaving a 0.

25mm (can be smaller) Leaving 100 microns On either side of the fluid Flow for clearance Surface tension or flatness of substrate can cause the fluid to flow this far Example of a System in

7 Jet vs. Needle Tight Packaging / Tight Keep-outs CL 28 gauge needle OD - 0.4mm ID 0.2mm 0.1mm jet nozzle 0.1mm stream CHIP CAP CHIP CAP 0.7mm (0.028 ) 0.4 wide fluid line Leaving a 0.15mm gap on either side stream +/- 50 Microns 14 mils 0.7mm (0.028 ) Underfill wet out Typically limited to 0.25mm (can be smaller) Leaving 100 microns On either side of the fluid Flow for clearance Surface tension or flatness of substrate can cause the fluid to flow this far Example of a System in Package (SiP) Worlds Smallest Global Positioning System (GPS) MMT 10mm x 10mm Package SIP with cover removed Dispense Tip Underfill Underfill Underfilled Devices 0.33 mm gap Between devices Smallest Standard Needle Only choice but has highly restricted fluid flow hence slow process Needle Chart 7

8 Understanding Fluid Flow Two Fluid Testing = Black Fluid = White Fluid Video on presentation Two Lines Two L shaped Lines Flex Circuits are Not Flat Vacuum / Heated Stage 8

Precision Height Sense for many pads Needle

5 mm to 3 mm Dispensing Speed Comparison

9 Precision Height Sense for many pads Needle Vs Jetting Needle 1 dot Jet Multiple dots Warp or elevation change no problem Typical jetting height 0.5 mm to 3 mm Dispensing Speed Comparison Needle v Jet 4 dots of corner bond adhesive Needle Jet Video on presentation 9

10 Material Flow Problems with Needles and Tight Spaces Typical problem with needle fluid flowing onto passive devices Jet Theory of Operation Video on presentation 10

11 Jet On the Fly Wetted area 0.25mm from die edge Video on presentation 1mm gap no bridging Jet On the Fly 10 mm Distance 30 m sec Time Number dots for a line length Lines Ultimate in speed Continuous line path with breaks Lines With Breaks 11

Jet Repeatability Mass (mg) (10 mg Slide Test) DJ-9K Jetting 15 14 13 12 11 10 9 8 7 6 5 0 20 40 60 80 100 Slides Material: Loctite 4531 Underfill Mean slide weight (mg) 10.16 Standard Error 0.

12 Jet Repeatability Mass (mg) (10 mg Slide Test) DJ-9K Jetting Slides Material: Loctite 4531 Underfill Mean slide weight (mg) Standard Error Median Standard Deviation Sample Variance Kurtosis Skewness Range 1.2 Minimum 9.5 Maximum 10.7 Sum 1016 Count 100 Largest(1) 10.7 Smallest(1) 9.5 Confidence Level(95.0%) Cpk(15%, 10mg) = 1.8 Smaller Wetted Areas = Higher Density Designs 12

13 Summary Jetting technology adds flexibility to the underfill process. The ability to save space and not coat surrounding components is very valuable Speed improvements of 2 to 4X are not uncommon with jetting High density designs are positioning the need for jetting technology Thank You Questions? 13

Jet Dispensing Underfills for Stacked Die Applications

Jet Dispensing Underfills for Stacked Die Applications Steven J. Adamson Semiconductor Packaging and Assembly Product Manager Asymtek Sadamson@asymtek.com Abstract It is not uncommon to see three to five