Frequently Asked Questions (FAQ) - Common Questions to FIDES Guides 2004 and 2009

Q: Page 45. There is some misunderstanding with "Area of application" options. In the table on the Page 39 in the column "Area of application" there are 3 options: Inhabited, Uninhabitable, Motor.
A: 

"Inhabited" shall always be used instead of "habitable".

Q: Page 50. On the Page 81 there are two types of the Tantalum Capacitors: Wet tantalum and Solid tantalum. In the table for the C_sensitivity factor (Page 50) there is only entry for Solid tantalum.
A: 

The same value of C_sensitivity shall be used for both types of tantalum capacitor.

Q: Page 60. The FIDES Guide defines the "high conductivity" and "low conductivity" of a board. However, the table displaying parameter K values shows "low conductivity" and "unknown conductivity".
A: 

Concerning the table, it should only display "high conductivity" and "low conductivity". Therefore, "conductivity unknown" should be replaced with "high conductivity". Furthermore, if the thermal conductivity of the board is unknown, it is recommended to choose a high conductivity.

Q: Page 60 & 61. In general, are there straightforward criteria to know if the board has a high conductivity or low conductivity?
A: 

If the conductivity is known, there is no problem since a limit value of 15W/m.K has been defined. Otherwise, "low conductivity" generally applies on boards which have surface metallization only (typically for microwave functions). A board which has more than two internal layers (power supply + ground), should be considered as a “high conductivity” board.

Q: Page 61. There shouldn’t be two columns for Rjc in the table, since this parameter does not depend on the board conductivity.
A: 

Actually, there is a mistake in the table concerning the active components cases: therefore, only six columns should be displayed in the page 61 table (case type, equivalent name, Np, Rjc, Rja with V=0m/s – Low conductivity and Rja with V=0m/s – High conductivity). Rjc “high conductivity” should never be used.

Q: Page 63-64 and 68-69. Tables for cases failure rates. These cases refers mostly to a product type, either integrated circuit or active components.
A: 

Yes. Unfortunately this is not possible with the current version of FIDES Mill V2004A tool.

Q: Page 67, page 70. Why is the Power-rated and not the Power-applied used for junction temperature calculations?
A: 

This is an inaccuracy. Of course the real applied power has to be taken for Tj calculation and not the rated power.

Q: Page 92. What is the definition of "routing class" of PCBs ?
A: 

The definition of the "Routing Class" of PCBs is described in the French standard NF C 93-713. The Routing Class characterizes the density of interconnection (and the tolerances for part placing). The following summary may be used:

 

 

Design values 1 2 3 4 5 6
Minimal Width of routed tracks (mm) 0,80 0,50 0,31 0,21 0,15 0,12
Minimal spacing between both tracks or pads (mm) 0,68 0,50 0,31 0,21 0,15 0,12

 

 

For a multi-layer PCB, the "Routing Class" is given by the layer with the highest density.

In a same layer, the routed area with the highest density defines the "Routing Class" of the layer.

For a complete definition of routing classes, refer to NF C 93-713.

 

Q: Page 93, 95. For all components Humidity factor in an operating phase = 0, only for PCB (Page 93) and Connector (page 95) there isn't such definition?
A: 

Yes PCB and connectors remain affected by humidity in operating phases (unlike the other components).

Q. Page 93. Why do the acceleration factor PRH for PCB have a reference of 40% instead of 70% for other item?
A: 

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