Surface mount quartz crystals

Paul Boughton

Surface mount frequency control components have been manufactured for more than 50 years. The earliest types were clock oscillators and metal cased microprocessor crystals with their leads pre-formed for circuit board placement; this had the distinct advantage of maintaining the component specification with no trade-off for different packaging materials or a reduced volume.

To achieve the modern high quality SMD products a number of technical problems had to be solved, including a totally automatic process for manufacturing and absolute cleanliness within the package. Cleanliness was of particular importance as sub-micron particles within miniature packages would have a significant effect upon quartz ageing. New materials were required to house SMD crystal blanks and provide a long-term hermetic seal.

To some extent a number of technical issues still exist for the production of SMD quartz crystals including the inability to accurately process the quartz wafer and to therefore provide the highest specifications; as a result the current smd crystals are limited to low level microprocessor specifications where applications are high volume and single frequency. Within this specific range of applications there is now the opportunity for semiconductor manufacturers to produce MEMS and NEMS devices and replace both the traditional quartz crystal devices and their smd equivalents.

Total Frequency Control provides a wide range of smd quartz crystals to industry worldwide in volume, R&D and prototype quantities and both standard and custom frequencies.

Applications include automotive such as the keyless entry systems and engine management, smart credit cards, animal tracking systems, telecommunications and digital instrumentation. Size ranges from 1.6 x 1.0mm up to 8.0 x 2.3mm in standard and custom frequencies.

This range includes the latest sub-miniature crystals produced by River Electronics, manufacturer of the smallest micro crystals in the world, along with the ubiquitous 32.768kHz crystal, which they reduced to the unbelievable footprint of 1.6 x 1.0mm with a height of just 0.5mm. This latest product has been developed also for the use in smart card applications where the crystal is imbedded within the thickness of the card as part of the control and security circuit. These micro crystals are also manufactured from 12~80MHz as smd AT cut fundamental designs in packages from 1.2 x 1.0mm and just 0.33mm tall and as micro smd oscillators from 1.5~400MHz with packages ranging from 1.6 x 1.2mm and 0.7mm in height and in conventional resistance weld leaded and pre-formed SMD HC-49/U03 units.

To satisfy precision applications TFC supplies its HC49/U (49SXF) package that maintains traditional qualities of metal packaged crystals as a low profile precision crystal in an SMD header package. Specifications can include temperature tolerance from ±5ppm, custom parameters and fast delivery; they are suitable for new prototypes or drop in replacements for HC-49 packages. Also XP/XJ smd packages are low profile and can be manufactured for standard and custom made frequencies, are low cost, and available in AT cut and BT cut

The challenge for the future is to manufacture high precision crystals in AT cut and SC cut in SMD packages.

TFC is based in Storrington West Sussex, UK.