An increasing common trend within the use of resistors for the Space market is the use of precision resistors, which enjoy lower values of a Temperature Coefficient of Resistance (TCR).
An increasing common trend within the use of resistors for the Space market is the use of precision resistors, which enjoy lower values of a Temperature Coefficient of Resistance (TCR).
Among the manufacturers offering these parts, Vishay Precision Group (VPG) foil resistors provide a wide range of options suitable for all kind of applications. For Space applications, the two following opportunities arise:
The references to be used for ordering each option are:
- Resistors tested following a reduced flow based on EEE-INST-002 from NASA (“Instructions for EEE Parts Selection, Screening, Qualification, and Derating”).
- Resistors tested following DSCC Military Drawings from DLA (Defense Logistics Agency).
From VPG foil resistors portfolio, resistor series VSMP provides a compelling case to compare both alternatives, as they are offered according to both options, even if they are not formally qualified. These series give a nominal TCR value of 0.2 ppm/ºC over the full military temperature range and a typical Load Life Stability on 2000h of 0.005%.
| VPG standard Type/Series | Testing iaw DLA DRAWING & MIL-PRF-55342 | Testing iaw EEE-INST-002 & MIL-PRF-55342 |
|---|---|---|
| VSMP0805 | DWG 07024 | Model 303134 |
| VSMP1206 | DWG 07025 | Model 303135 |
| VSMP1506 | DWG 03010 | Model 303136 |
| VSMP2010 | DWG 06001 | Model 303137 |
| VSMP2512 | DWG 06002 | Model 303138 |
Concerning the testing, the first row of the table can be used to make an excellent example of the similarities and differences in the screening on each option:
a. For DSCC 07024, the conformance inspection consists of Group A inspection (only for ER level parts; subgroups 1 & 3 and PPM reporting are not applicable) and Group B following MIL-PRF-55342:
b. On the other hand, the testing for Model 303134 includes the following:
EEE-INST-002 (Table 2A Film/Foil, Level 1) 100% Tests/Inspections
- Pre-cap Visual Inspection
- RC Record
- Thermal Shock
- Power Conditioning
- Final Inspection
- Visual Inspection
- Mechanical Inspection
EEE-INST-002 (Table 3A Film/Foil, Level 1) Destructive Tests
- Solderability
- TCR (-55ºC/+25ºc/+125ºC
- Low-Temperature Storage
- Low-Temperature Operation
- Short – Time Overload
- Resistance to Soldering Heat
- Life
- Mechanical Inspection
As can be observed, some of the tests, as Thermal Shock, Solderability, TCR and Short-Time Overload performed on both of the flows. In contrast, others, such as pre-cap inspection, power conditioning and life tests, are performed only on the flow based on EEE-INST-002.
Further details on both flows and additional resistors series available from the manufacturer can be found at:
