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HTCR [ppm/K]
70
60
50
40
30
20
10
0
-10
-20
-30
CrNi
20 Ohm/sq 50 Ohm/sq 100 Ohm/sq
Al2O3
LTCC
Fig. 12: HTCR of CrNi on LTCC and alumina for
various resistances (l/b=107:1)
HTCR [ppm/K]
0
-20
-40
-60
-80
-100
-120
TaN
20 Ohm/sq 50 Ohm/sq 100 Ohm/sq
Al2O3
LTCC
Fig. 13: HTCR of TaN on LTCC and alumina for
various resistances (l/b=107:1)
The principally higher thickness of Tantal
Nitride compared with CrNi lead to more stable
conditions. The measured HTCR-values of TaN on
LTCC do not differ from those on Al2O3, (usually
from -90 to -110 ppm /K).
Laser trimming of thin film resistors could
be carried out without any difficulties. Fig. 14 shows
a resistor with the geometry of l = 10,7 mm and b =
100 µm after trimming. Tolerances in the range of
± 1% can be achieved. First stability tests (1000 h @
150 °C) have already indicated positive results.
Fig. 14: Laser trimmed thin film CrNi resistor
Summary and Outlook
Design constraints for hermetic packages
were determined. It has been shown that thermal via
designs have an impact on module hermeticity. Cost
effective lead free solder was successfully used for
sealing LTCC packages. The package designs allow
RF transitions which are capable up to frequencies
over 40 GHz.
Regarding thin film resistors on LTCC it can
be concluded that TaN-resistors are very suited
because of the quite comparable behaviour to
alumina. In general, also CrNi resistors can be applied
on LTCC 951 with the exception of the low resistance
value.
Future work within the project will focus on
the thermal assessment of hermetic packages and the
evaluation of different packaging concepts in terms of
RF and thermal management.
Acknowledgements
The authors would like to thank the German
Government for the financial support. The work
carried out in the project Keramis is funded by the
BMBF under the project number 50 YB 0316.
References
[1] M. Ray Fairchild et al.: LTCC Technologies for Harshenvironment
Automotive Applications Utilizing Soldered
Interconnections, Proceedings of the 37 th International
Symposium on Microelectronics, Nov. 14-18, 2004, Long
Beach, CA.
[2] Dan Amey, Mimi Keating: Thermal Performance of 943
Low Loss Green Tape LTCC with Thermal Via and Internal
Metallization Enhancements, Proceedings of the 2004
Ceramic Interconnect Technology Conference, April 26-28,
2004, Denver/CO, USA.
[3] Yasunari Ukita et al.: Lead free die mount adhesive
using silver nanoparticles applied to power discrete
package, Proceedings of the 37 th International Symposium
on Microelectronics, Nov. 14-18, 2004, Long Beach, CA.
[4] Ruben Perrone et al.: Development and Evaluation of
Photodefined Elements for Microwave Modules in LTCC
for Space Applications, 14 th European Microelectronics and
Packaging Conference, June 12-15, 2005, Brugge/Belgium.
[5] Günter Reppe et al.: Development and Evaluation of
Fine Line Structuring Methods for Microwave Packages in
Satellite Applications, 14 th European Microelectronics and
Packaging Conference, June 12-15, 2005, Brugge/Belgium.