1. ELong PolyRAD q P1501 Effects of Device Packaging and PC Board Materials on Radiation Dose in the Die Edward R. Long, Jr. Longhill Technologies, inc. Waynesboro, VA 540-363-0104 LonghillTechnologies@PolyRAD.net 2004 MAPLD Ronald Reagon Building & International Trade Center Washington, DC September 8-10, 2004 Session P, Paper 150

2. ELong PolyRAD q P1502 Presentation Outline  Aspects of spacecraft and on-board electronics that contribute to radiation shielding  What was modeled for total dose  A single electronics board populated with a 3 X 5 array of microelectronic devices  whose packaging are plastic or ceramic (with and without lids),  each of which are represented with several degrees of supplemental shielding  and the board is studied with and without a 4-oz copper ground plane  Dose-at-the-die for the array of devices for two board locations in two spacecraft designs  Three orbital environments: GSO, GTO, and SSO  Discussion of the results  Effects of packaging, PCB, and shielding on TID  Implications for dosimeter measurements

3. ELong PolyRAD q P1503 Aspects of Spacecraft and On-board Electronics That Contribute to Radiation Shielding  Aspects discussed in an earlier presentation 1  Board location  Where on the spacecraft  Which board in an ordered stack of boards  Board Orientation  Device position  Location on the board  Adjacent devices  The structure, materials, and location of other on-board components  Aspects discussed in this presentation  Device packaging materials  Plastic  Ceramic  PCB materials  No ground plane  4-0z Cu ground plane  Supplementary shielding  10-mil, 20-mil, 40-mil, and 80-mil PolyRAD  Two inward-facing board locations (between –X shear panel and –X battery)  Near –X shear plane  Near –X battery 1. - Long, Edward R., Jr., Modeling the Requirements for Radiation Shielding, 2003 MAPLD International Conference, Washington, DC, September 9-11, 2003

4. ELong PolyRAD q P1504 Description of the Dose Modeling  Two spacecraft designs  A Generic spacecraft 1  Three-Quarter view  Intrinsic shielding equivalent to 0.135-in aluminum  Thin-walled version of the generic spacecraft  Intrinsic shielding equivalent to 0.040-in aluminum 1. - Long, Edward R., Jr., Modeling the Requirements for Radiation Shielding, 2003 MAPLD International Conference, Washington, DC, September 9-11, 2003 Exterior instruments Solar panel Tank support panel Shear panel Anti-buckle panel -X Battery Internal component Instrument support panel Tanks

5. ELong PolyRAD q P1505  Orbits  GSO: 35800 km x 35800 km x 0 deg  GTO: 36000 km x 300 km x 7 deg  SSO: 800 km x 800 km x 98 deg  Single electronics board consisting of a 3 X 5 array of copies of a device, modeled with plastic and ceramic encapsulation (packaging). Description of the Dose Modeling (continued) Column 1 (plastic encapsulate) Column 2, (alumina encapsulate, withkovar lid) Column 3, (alumina encapsulate, without kovarlid) Non-shielded Row 10-milPolyRAD q Shielded row 0.062-in FR4 0-oz or 4-oz copper ground plane 10-milPolyRAD q Shielded row 10-milPolyRAD q Shielded row 10-milPolyRAD q Shielded row Sketch is not to scale kovarlid die Column 1 (plastic encapsulate) Column 2, (alumina encapsulate, withkovar lid) Column 3, (alumina encapsulate, without kovarlid) Non-shielded Row 10-milPolyRAD q Shielded row 0.062-in FR4 0-oz or 4-oz copper ground plane 20-milPolyRAD q Shielded row 40-milPolyRAD q Shielded row 80-milPolyRAD q Shielded row kovarlid die

6. ELong PolyRAD q P1506  Cross section of modeled device, shown using ceramic encapsulation Description of the Dose Modeling (continued) 0.295” 0.705” 0.300” 0.208” 0.197” 0.201” 0.123” 0.042” 0.157” 0.039” x 0.039” 0.087” 0.027” X Y X Z Kovar lid: 0.455” x 0.274” x 0.010” Top and side views (Kovar lid removed) When in place, the lid is centered on the top of the device

7. ELong PolyRAD q P1507 Discussion of the Results  External and internal annual doses for solar maximum conditions 1 in three orbit types and a PCB with no (0-oz) ground plane 1.: Trends for solar minimum conditions are the same 2 : 40-GSO-0Oz-Batt represents the 40-mil spacecraft in GSO having an electronics board that has no rear ground plane and located near the –X battery 3: An external location on the top of the spacecraft 4: An internal location inside the Spacecraft next to the +Z,-Y corner of the electronics board 5. A location on the populated face of the electronics board, near the +Z,-Y corner of the electronics board NOTE: The board’s populated side faces the +X direction, i.e. towards the center of the spacecraft.  Comments  The additional shielding provided by the 135-mil spacecraft varies with the energy distributions of the electrons and protons within the orbit. It is a factor of approximately 30 for GSO, 15 for GTO, and 8 for SSO.  The effect of the location in the spacecraft (at the negative-X axis’s battery or shear panel) on the dose is a complex consideration that depends on the exposure’s solid angle, exterior panel thickness, and adjacent interior components.  The PCB (without a 4-Oz ground plane on its backside) reduces the dose by an additional factor of 2. Although this amount of dose reduction is not sufficient in most cases it does indicate that the board material and its sizing should be included as part of the dose modeling. 40-mil Spacecraft, rad(Si)40-GSO-0oz-Batt 2 40-GSO-0oz-Shear40-GTO-0oz-Batt40-GTO-0oz-Shear40-SSO-0oz-Batt40-SSO-0oz-Shear OUTSIDE SPACECRAFT 3 1.25E+09 8.05E+09 2.74E+052.78E+05 INSIDE SPACECRAFT 4 9.18E+058.18E+051.93E+061.86E+061.08E+049.18E+03 ON SURFACE OF BOARD 5 5.06E+052.09E+051.05E+065.45E+055.95E+033.24E+03 135-mil Spacecraft, rad(Si)135-GSO-0oz-Batt135-GSO-0oz-Shear135-GTO-0oz-Batt135-GTO-0oz-Shear135-SSO-0oz-Batt135-SSO-0oz-Shear OUTSIDE SPACECRAFT1.24E+09 8.01E+09 2.69E+05 INSIDE SPACECRAFT2.62E+042.86E+041.19E+051.25E+051.18E+031.35E+03 ON SURFACE OF BOARD1.66E+041.22E+047.78E+045.22E+048.15E+027.90E+02

8. ELong PolyRAD q P1508 Discussion of the Results (continued) ON SURFACE OF BOARD, rad(Si) 40-GSO- 0oz–Batt 40-GSO- 0oz-Shear 40-GSO- 4oz-Batt 40-GSO- 4oz-Shear 40-GTO- 0oz-Batt 40-GTO- 0oz-Shear 40-GTO- 4oz-Batt 40-GTO- 4oz-Shear 40-SSO- 0oz-Batt 40-SSO- 0oz-Shear 40-SSO- 4oz-Batt 40-SSO- 4oz-Shear SOLAR MIN5.05E+052.08E+055.20E+052.39E+057.57E+053.85E+057.65E+054.29E+052.80E+031.58E+032.50E+031.44E+03 SOLAR MAX5.06E+052.09E+055.21E+052.40E+051.05E+065.45E+051.06E+066.15E+055.95E+033.24E+035.18E+032.90E+03 ON SURFACE OF BOARD, rad(Si) 135-GSO- 0oz-Batt 135-GSO- 0oz-Shear 135-GSO- 4oz-Batt 135-GSO- 4oz-Shear 135-GTO- 0oz-Batt 135-GTO- 0oz-Shear 135-GTO- 4oz-Batt 135-GTO- 4oz-Shear 135-SSO- 0oz-Batt 135-SSO- 0oz-Shear 135-SSO- 4oz-Batt 135-SSO- 4oz-Shear SOLAR MIN1.57E+041.12E+041.54E+049.48E+035.89E+043.92E+046.05E+043.91E+045.23E+025.02E+025.22E+024.78E+02 SOLAR MAX1.66E+041.22E+041.63E+041.05E+047.78E+045.22E+047.98E+045.18E+048.15E+027.90E+028.13E+027.43E+02  Comments  The dose reduction due to board location (outboard near the battery versus inboard near the shear panel) is larger for the 40-mil spacecraft and varies more with the orbit. Thus PCB’s contribution to the total shielding is more significant for smaller spacecraft.  The additional shielding provided by the 4-Oz copper ground plane is not consequential for either the 40-mil or the 135-mil spacecraft.  Annual dose on the surface of the board, with and without a ground plane (1), for the two board locations (2), and the three orbits. (1)– “0oz” means without ground plane and “4oz” means 4-oz ground plane (2)- “Batt” means located near the battery and “Shear” means near the shear panel

9. ELong PolyRAD q P1509 Discussion of the Results (continued)  Dose reduction effects of plastic and ceramic encapsulation  Comments  Dose modeling typically models the dose inside the spacecraft (bar 1) and doesn’t include device encapsulation  For the 40-mil spacecraft, plastic encapsulation (bar 2) reduces the dose an additional order of magnitude in all 3 orbit types. The ceramic encapsulation (bar 3) reduces the dose 2 additional orders of magnitude, except for the SSO.  For the 135-mil spacecraft, the plastic encapsulation (bar 2) reduces the dose by a factor of ~5 and the ceramic encapsulation (bar 3) reduce the dose an additional order of magnitude.  The trends for the effects of encapsulation are also true for near the shear panel and for solar minimum conditions at both locations. (data not shown)  The additional shielding provided by encapsulation may explain flight cases for which parts do not fail even though gamma radiation tests suggest the opposite. 40-mil Spacecraft135-mil Spacecraft

10. ELong PolyRAD q P15010 Discussion of the Results (continued)  Additional dose-reduction provided by PolyRAD q 1 for plastic encapsulated (packaged) die  Comments  These data are for plastic encapsulated (packaged) die adjacent to the –X battery inside the 40-mil spacecraft. Conventional representation of the dose reduction provided by a supplemental shielding, as shown in the next slide, does not include the encapsulation material.  The limit for dose reduction is achieved by a shield thickness of approximately 20 mils. This is 25% of the thickness indicated by conventional representations (see the next slide) and thus a significant weight savings. 1 – PolyRAD is an advanced radiation shielding material developed under a NASA SBIR contract

11. ELong PolyRAD q P15011 Discussion of the Results (continued)  Conventional methods for representations of the dose-reduction provided by PolyRAD q 1  Comments  On the left: Just PolyRAD, thus the dose for zero thickness is that of bare (neat) space  On the right: PolyRAD + 40-mil aluminum, thus the dose for zero thickness is that behind 40-mil aluminum.  The limit for dose reduction requires from 80- to 160-mil thick PolyRAD. Thus conventional modeling may overestimate the amount of required supplemental shielding. This could be a error for small, weight-critical spacecraft. (Conventional modeling does not account for shielding provided by the spacecraft/internal component structure and the material type and size for electronic boxes, PCB, and die encapsulation.) 1 – PolyRAD is an advanced radiation shielding material developed under a NASA SBIR contract No spacecraft40-mil spacecraft

12. ELong PolyRAD q P15012 Discussion of the Results (continued)  Dosimetry implications of encapsulation  Comments  The ceramic-packaged die in this study is similar to a candidate radfet package for space flight dosimetry.  The measured dose predicted by the modeling (kovar lid in place) is from 1 to 2 orders of magnitude less than on the board surface:  For 40-mil spacecraft – Modeled measured dose is from 1 to 8 percent of that at the board  For 135-mil spacecraft – Modeled measured dose is from 1 to 4 percent of that on the board  Removal of the Kovar lid significantly reduces the dosimetry error.

13. ELong PolyRAD q P15013 Summary Remarks  This study modeled the dose-at-the-die for an array of copied devices on a single board at two locations in two different generic spacecraft designs (40-mil and 135-mil) for GSO, GTO, and SSO radiation environments.  Observations from the modeled doses:  PCB (0.062”) reduced the dose approximately 50 %  4-oz Copper ground planes did not have a significant effect on the dose.  For the 40-mil design the location of the board varied the dose as much as 50%.  The combined effect of the spacecraft structure, internal adjacent components, the PCB and its location, and the device encapsulation reduced the dose two orders-of magnitude for GSO and GTO and a little more than one order-of-magnitude for the SSO.  The amount of supplemental shielding (in this study PolyRAD) to attain low doses using the detailed approach to modeling in this study is 25 % or less than that determined from conventional modeling. This indicates that significant savings in the mass cost of supplemental shielding are possible.  The effects of encapsulation material can introduce significant dosimetry errors for devices such as radfets.