Nemco Electronics Performance Info - Manual (Page 12)

General Performance Information
z Mechanical properties
Tantalum chip capacitors are mechanically robust, meeting requirements for high speed insertion machines and the needs of
most automotive and aerospace applications. The performance specifications:
Acceleration 10 g (98.1 m/s 2 )
Vibration severity 10 to 2000 Hz, 0.75mm of 10 g (98.1 m/s 2 )
Shock Trapezoidal Pulse 10 g (98.1 m/s 2 ) for 6 ms
Adhesion to substrate Nemco chip components meet IEC 384-3. This requires a minimum adhesive to substrate strength
of 5 Newtons.
Resistance to substrate bending and expansion Because the component has compliant leads, thermal mismatch
between the component and substrate (ceramic, FR4, etc.) or bending of the substrate itself, will not normally give rise to
stress at the solder joint and will enhance the temperature cycling capability of the finished board.
Solderability Meets the requirements of IEC 68 2.20 Test Ta and MIL-STD-202, Method 208.
Stand off and glue pad The glue-pad on the PCT and LSR types aid high volume insertion: the surface of the pad is
etched to provide a strong mechanical key to the glue, and the reduced clearance allows the use of ultraviolet cured epoxies.
For the A, B, and P cases, the stand-off is 0.05±0.05 mm; for C, D, and H cases, it is 0.1±0.1 mm.
Flammability UL Rating UL94 VO, Oxygen Index 35%. Epoxy, Hysol MG 33.
Resistance to board cleaning Nemco tantalum chips have excellent solderability characteristics and are compatible with
mildly activated (RMA) or pure resin flux systems. The use of high acidity fluxes must be avoided. The encapsulation and
termination materials are resistant to immersion in boiling solvents such as: Freon TMS and TMC, Trichloroethane, Methylene
Chloride, Isopropyl alcohol (IPA), etc., up to 50°C. If ultrasonic cleaning is to be applied in the final wash stages the
application time should be less than 5 minutes with a maximum power density of 9 mW/cc to avoid damage to terminations.
Care should also be taken to ensure that boards are firmly held and that adjacent boards are not allowed to contact each other.
Nemco tantalum chips are also compatible with newer aqueous and semi-aqueous processes.
Thermal Management.
The heat generated inside a tantalum capacitor in a.c. operation comes from the power dissipation due to ripple current. The
heat will be transferred from the outer surface by conduction. How efficiently it is transferred from this point is dependent on
the thermal management of the board.
Power dissipation ratings are based on free-air calculations. These ratings can be approached if efficient heat sinking and/or
forced cooling is used.
In practice, in a high density assembly with no specific thermal management, the power dissipation required to give a 10°C
rise above ambient may be up to a factor of 10 less. In these cases, the actual capacitor temperature should be established
(either by thermocouple probe or infra-red scanner) and if it is seen to be above this limit it may be necessary to specify a
lower ESR part or a higher voltage rating.