1 / 24

Die Attach Process Development Using B-stageable Epoxies

Die Attach Process Development Using B-stageable Epoxies. Elgin F Bravo May 11th 2001 Advisors Dr. R. Chung Randall Walberg SJSU NSC. Motivation. Reduce package size

Thomas
Download Presentation

Die Attach Process Development Using B-stageable Epoxies

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Die Attach Process Development Using B-stageable Epoxies Elgin F Bravo May 11th 2001 Advisors Dr. R. Chung Randall Walberg SJSU NSC

  2. Motivation • Reduce package size • Ability to wirebond close to edge of die • Easy to die attach small dies • Dies smaller than 1mm2 • Reduce cycle time • Increase profits • Innovative • New to industry

  3. Outline • Objectives • Last semester accomplishments • Background on B-Stage epoxies • Literature review • Percent conversion • Infrared Absorption Spectroscopy • Moisture Sensitivity Level • MSL results • Conclusion • Future work

  4. Objectives • Determine process feasibility and ease of manufacturing • Coating of die with b-stage epoxy • Die attach die onto leadframe • Elimination of epoxy bleed • Study moisture and heat sensitivity of B-stageable epoxies when used as die attach materials in leadless leadframe packages.

  5. 1mm 1mm B-Stage epoxy Standard epoxy Last Semester Accomplishments

  6. Background on B-stageable Epoxies • A-stage --> unpolymerized --> 0% conversion • B-stage --> some polymerization --> 28 ~ 45 % conversion • C-stage --> mostly polymerized --> 90% conversion

  7. Literature Review • Percent conversion determines bond reliability • Higher degree of conversion lower bond reliability • Lower degree of conversion higher bond reliability

  8. Determining % Conversion • Differential Scanning Calorimetry (DSC) • dX/dt = K(T) x f(X) • k(T) reaction rate constant • X fractional conversion • t cure time • Infrared Absorption Spectroscopy • Epoxide + Hardener = polymer chain

  9. NaCl disk, 2.5 mm thick Detector Thin layer of epoxy ~ 0.5mm Infrared Absorption Spectroscopy E = h  = c/  = 2.5e-4 to 25e-4 cm

  10. % T R A N S M I T T A N C E Infrared Spectroscopy Functional group

  11. Chemical Reaction in Epoxies O || R1 - C = C - R2 + R3 - C - O - O - H ---> Alkene Peroxyacid O H / \ . . | • R1 - C - C - R2+ H - N - R3---> R1 - C - CH2 - R2 | | H H2N - R3 Epoxide Amine Polymer chain (hardener)

  12. Components in B-stageable Epoxies

  13. CH2 CH CH2 Bond Structure of Epoxide Molecules BisphenolA/ Epichlorohydrin epoxy Cresol novolac epoxy

  14. Infrared Transmittance as function of Curing TimeSumitomo 4291 Epoxide C-C Amine (N-H) Carboxyl (COOH)

  15. Infrared Transmittance as function of Curing Time Epoxide C-C Amine (N-H) Carboxyl (COOH)

  16. Curing time & temperature

  17. Moisture Sensitive Levels • Level 1: 168 hrs 85C / 85% Relative Humidity (Excellent) • Level 2: 168 hrs 85C / 60% Relative Humidity (Good) • Level 2A: 150 hrs 60C / 60% Relative Humidity (Satisfactory) • Parts go through reflow oven reaching a max temperature of 235C • Packages assembled onto PCB are reflowed at ~ 220C

  18. Leads Die Cu substrate Top sonoscan view of a Package

  19. Sonoscan Results MSL 1 Front view Back view

  20. Sonoscan Results MSL 2 Front view Back view

  21. Sonoscan Results MSL 2A Front view Back view

  22. Conclusion • Process was concluded to be feasible • Die coating • Die attach • Elimination of epoxy bleeding • Infrared absorption spectroscopy might not be reliable for this type of study • Both B-stageable epoxies fail all three Moisture Sensitivity Levels

  23. Future Work • Work together with suppliers to improve MSL rating to at least MSL 2 • Thermal modeling • Determine how well epoxy dissipates heat • Electrical testing • Determine electrical conductivity of epoxy

  24. Acknowledgements • Dr. Richard Chung • Randall Walberg • Dr. Roger Terrell • National Semiconductor

More Related