1. Moisture effects in PEMs intended for space applications. NEPP mid-year review. Alexander Teverovsky, Ph.D QSS/Goddard operations Alexander.A.Teverovsky.1@gsfc.nasa.gov

2. 4/09/02 NEPP meeting2 No moisture in space. Do we have any problems? Mechanism Degradationconditions Ground phaseIn space CorrosionRH > 70%, bias- Popcorning Assembly,  m>0.1% - Leakage currentRH > 70 %- Charge instabilityRH > 50 % ?T? SwellingRH > 50 %Shrinkage Avoid high humidity Ensure reliability for Gnd phase Avoid high humidity Ensure reliability for Gnd phase D(T)

3. 4/09/02 NEPP meeting3 Purpose of work (two subtasks): I.Analyze moisture evolution in PEMs to develop risk mitigation measures and techniques. II.Evaluate moisture swelling effects in linear devices. Purpose of presentation : To discuss the problem and our approach. To report major achievements. To suggest future plans. Outline: I.Moisture diffusion characteristics. How to measure and how to use? II.Moisture swelling/shrinkage in MC. III.Environmental hysteresis in MC & linear devices

4. 4/09/02 NEPP meeting4 Conventional D(T) measurements: time domain T = T i D(T) = D o exp(-U/kT) DiDi D(T) in literature: Kitano’88?

5. 4/09/02 NEPP meeting5 New D(T) technique: temperature domain Equipment: TGA or T-chamber

6. 4/09/02 NEPP meeting6 D(T) measurement results. Saturation at 85  C/100%RH/168hr Mfr.:ActelV3SemiAMDXILINX Package: QFP144QFP160PLCC32QFP240 DC: 9505965295509608 dM , % 0.520.440.490.43 U, eV 0.50.450.310.41 D 20, sm 2 /s 3E-92.4E-93.2E-84.5E-9 D 85, sm 2 /s 1.2E-76.9E-83.2E-79.4E-8 D 130, sm 2 /s 7.8E-73.7E-71E-64.3E-7

7. 4/09/02 NEPP meeting7 In-situ D(T) technique. Areas of application. Lot characterization of molding compound. (ROBOCOTS: need rapid assessment methods) Evaluation of moisture leaks along the leads of a plastic package. (CSAM: gaps of > 0.1  m) Virtual qualification of moisture content evolution during pre-launch period. HAST alternative. (application-tailored testing). Calculation of characteristic times of moisture diffusion:  (T) = 0.85h 2 /D(T)

8. 4/09/02 NEPP meeting8 Bake-out conditions. Packagethickness40 o C125 o C150 o C DIP-243.8 mm 1929 (1608-1632) 57 (48) 26.5 DIP-83.2 mm 1368 (1608-1632) 40.5 (48) 18.8 PQFP-442 mm 534 (504-1632) 16 (18-48) 7.3 PLCC-323 mm 1202 (1608-1632) 36 (48) 16.5 TSOP-321 mm 134 (120-456) 4 (4-14) 1.8 Calculated  (hrs) and JEDEC recommendations (x-x).

9. 4/09/02 NEPP meeting9 Do we need HAST? Stewart Peck [86]: HAST: 1. biased and unbiased ($$$ and $) 2. JEDEC – 96 hrs, NAVSEA SD18 –150 hrs, projects – 250 hrs 3. 130 o C > oper.T 4. Power parts? HAST: 1. biased and unbiased ($$$ and $) 2. JEDEC – 96 hrs, NAVSEA SD18 –150 hrs, projects – 250 hrs 3. 130 o C > oper.T 4. Power parts? RH = P a /P s (T)

10. 4/09/02 NEPP meeting10 Do we need HAST alternative? Alternative: Unbiased HAST => (ionic activation) + HTB stress Alternative: Unbiased HAST => (ionic activation) + HTB stress The equilibrium constant: In a medium with low  : Ionic dissociation in polymer:

11. 4/09/02 NEPP meeting11 Bias HAST alternative: Unbiased HAST + HTB D(T) dataPckg type C(t,x) calculations Test conditions: T/RH/t HAST, T/t HTB Acceleration factor

12. 4/09/02 NEPP meeting12 Part II. Moisture swelling. Is it important?   A  E  [(  MC -  LF )  T +  m],  - hygroscopic expansion coefficient (rare to find in literature). At  =0.1-0.4 and  m~0.5%, the strain is equivalent to deformation at  T~30-120 o C. How to measure  ? Conventional techniques: Instrumental microscope (poor accuracy on PEMs); Moire interferometry (CALCE – special equipm., grating corrosion); Strain gage (corrosion); Suggestion: Hygroscopic weighting – simple, accurate, fast, in-situ.

13. 4/09/02 NEPP meeting13 Hygroscopic weighting technique Necessary equipment: Balance ±0.1 mg; Beaker; Piece of wire; Liquid. (low molecular weight perfluoropolyether fluid, 1.77 g/cc, T b = 175 o C) Archimedes of Syracuse Born: 287 BC in Syracuse, Sicily

14. 4/09/02 NEPP meeting14 Hygroscopic weighting technique Standard deviation: 3 to 5 % In-situ:  MC  (0.8-0.9)  pac

15. 4/09/02 NEPP meeting15 High T exposure shrinks packages? No popcorning. Is SMT a reliability risk? Qualification? No popcorning. Is SMT a reliability risk? Qualification?

16. 4/09/02 NEPP meeting16 Part III. Environmental hysteresis in PEMs Assumption:  Linear devices are most sensitive to swelling/shrinkage effects and are known HAST failures. Parts:  Several types of Vref, Opamp, DAC, ADC in different plastic and ceramic packages used in NASA projects have been purchased. Measurements:  ATE A540. Capabilities restored. Programming is ongoing.  A set-up for high precision measurements.

17. 4/09/02 NEPP meeting17 Set-up block-diagram PC-based System for linear devices: I =>pA range V=>µV range (ppm) T=> -120 to +200 °C Automatic switching, measurements and recording Reliability precursors? Cherry picking? Reliability precursors? Cherry picking?

18. 4/09/02 NEPP meeting18 Temperature hysteresis Mfr. data? 20 ppm/1000 hr Mfr. data? 20 ppm/1000 hr

19. 4/09/02 NEPP meeting19 Vref errors in ADC, DAC Temperature effect: ~ 50 – 200 ppm LT hysteresis: ~ 150 – 300 ppm Radiation effects [AD2710, JPL’97]: Co60, 100 krad(Si): ~ 150 ppm protons, 200 MeV, 45 krad(Si): ~ 500 ppm LT hysteresis causes significant error

20. 4/09/02 NEPP meeting20 Effect of external mechanical stress External stress: no additional LT hysteresis

21. 4/09/02 NEPP meeting21 Relaxation at RT after LT exposure Relaxation: RT: >1200 hrs; 85 o C: minutes; 75 o C & 55 o C ? Questions: Multiple TC? T & duration of exposure? Mechanical integrity? Relaxation or switching? Questions: Multiple TC? T & duration of exposure? Mechanical integrity? Relaxation or switching?

22. 4/09/02 NEPP meeting22 Moisture hysteresis 2h = 1.5 mm D85=4e-8 cm2/s  = 0.85h 2 /D  35 hr Moist. Hysteresis: 85/85 => 150-250ppm Moist. Hysteresis: 85/85 => 150-250ppm

23. 4/09/02 NEPP meeting23 Vacuum hysteresis Vacuum hysteresis: dV > 50-100 ppm; t > 1500 hrs Vacuum hysteresis: dV > 50-100 ppm; t > 1500 hrs 2h = 1.5 mm D20 = 3E-9 cm2/s  = 0.85h 2 /D  1500 hr

24. 4/09/02 NEPP meeting24 Effect of preconditioning on LT hysteresis LT hysteresis: - Humid cond. ~ 170 ppm - Dry cond.: ~ 265 ppm synergistic effect of T & vacuum? synergistic effect of T & vacuum? Possible cause of HAST/PCT failures

25. 4/09/02 NEPP meeting25 Expected results in 2002: Two in-situ methods for moisture characterization of molding compounds in PEMs. Analysis of moisture diffusion in different PEMs and recommendations for moisture-prevention measures. Analysis of environmental hysteresis effects caused by LT, moisture, and vacuum conditions in Vref PEMs. Deliverables: papers, presentations, recommendations.

26. 4/09/02 NEPP meeting26 Suggestions for 2003 Analysis of environmental hysteresis (T, RH, vacuum) in MC and advanced linear PEMs (opamps, AD, DA converters). Experimental and theoretical analysis of effectiveness of HAST for space applications. Development of adequate accelerated testing technique. Virtual qualification of moisture evolution in PEMs to mitigate risks with flight parts.