Micro Crystal
Low Power Clock Oscillator 32.768 kHz
OV-7605-C8
June 2017
18/20
Rev. 1.0
HANDLING PRECAUTIONS FOR MODULES WITH EMBEDDED CRYSTALS
6.3.
The built-in tuning-fork crystal consists of pure Silicon Dioxide in crystalline form. The cavity inside the package is
evacuated and hermetically sealed in order for the crystal blank to function undisturbed from air molecules,
humidity and other influences.
Shock and vibration:
Keep the crystal / module from being exposed to
excessive mechanical shock and vibration
. Micro Crystal
guarantees that the crystal / module will bear a mechanical shock of 5000 g / 0.3 ms.
The following special situations may generate either shock or vibration:
Multiple PCB panels -
Usually at the end of the pick & place process the single PCBs are cut out with a router.
These machines sometimes generate vibrations on the PCB that have a fundamental or harmonic frequency
close to 32.768 kHz. This might cause breakage of crystal blanks due to resonance. Router speed should be
adjusted to avoid resonant vibration.
Ultrasonic
cleaning -
Avoid cleaning processes using ultrasonic energy. These processes can damages
crystals due to mechanical resonance of the crystal blank.
Overheating, rework high temperature exposure:
Avoid overheating the package. The package is sealed with a seal ring consisting of 80% Gold and 20% Tin. The
eutectic melting temperature of this alloy is at 280°C. Heating the seal ring up to >280°C will cause melting of the
metal seal which then, due to the vacuum, is sucked into the cavity forming an air duct. This happens when using
hot-air-gun set at temperatures >300°C.
Use the following methods for rework:
Use a hot-air- gun set at 270°C.
Use 2 temperature controlled soldering irons, set at 270°C, with special-tips to contact all solder-joints from
both sides of the package at the same time, remove part with tweezers when pad solder is liquid.
