In the Quartz Crystal manufacturing industry, there is a long standing, and industry accepted, practice of using the term “HC-49” callout to describe types of standard packages used in the production process of Quartz Crystal manufacturing. This practice can produce confusion, and lead to a basic question as follows:
“When noticing the term “HC-49” in a Crystal description, how can I be certain this product is the proper callout according to whether my application calls for either a Surface Mount Crystal, or a Through Hole Crystal?”
The answer to this question requires an understanding of why the industry uses this callout, and then an understanding of how to best distinguish between calling out a Surface Mount versus Through Hole Crystal Package in the BOM description field.
The “HC-49″ portion of a Quartz Crystal description is an industry call out for any device using the same (or similar) “metal can” in the production process. In this case, it is common to see the “HC-49″ Through Hole device and the “HC-49” Surface Mount device with the same “HC-49” (written as either HC49 or HC-49) callout in the description.
This “root” part number classification is based on a historical practice that became widely accepted before Surface Mount devices became the predominant device preferred by end users. The “HC-49” callout was a long established industry callout to describe the dimensions associated with the most common industry package of the original Through Hole package used in Crystal production. In order to gain advantages in cost, this standard package was adopted by the industry, and it became the most widely used package in history up until improvements in size and features were later introduced. This package was widely accepted as the “HC-49U” package, which was, by today’s size standards, a very large device.
Over time, the HC-49U package began to take on different forms in order to meet the demands of global OEM package preferences. One obvious adjustment the was required by end users for a smaller package, while still maintaining the Through Hole characteristics, and sharing of the same pitch (distance between leads). In response, the metal can height was shortened, and the result was an industry standard device commonly identified as the “HC-49US” package. In this case the addition of the “S” to the base callout was intended to identify the “short” version of the HC-49U. The HC-49US device had a body height of less than half that of the HC-49U.
As the HC-49US package gained momentum in production, it quickly overtook the previous HC-49U package as the most widely produced industry standard Through Hole Crystal in the world. To this day, the HC-49US package remains the most widely produced Through Hole Crystal package.
As further pressure mounted for an inexpensive Surface Mount device to meet the demands of a worldwide OEM transition to Surface Mount Technology, the HC-49US package was again adapted utilizing a slightly different lead frame resulting in a Surface Mount device. The Surface Mount version of the HC-49US package was then introduced bearing the same root callout as the original Through Hole device. By molding a base for the lead frame to attach to, and by adding a few manufacturing steps, the original Through Hole device was easily adapted to Surface Mount Technology. The result was an industry callout of “HC-49USM,” or “HC-49USMD” where the addition of the “M” was used to identify the Surface Mount callout. Today, manufacturers of Quartz Crystals commonly use either “HC-49USM,” or “HC49USMD” to designate the device as the Surface Mount version of HC-49US. The HC-49USM (or HC-49USMD) is now the highest volume Crystal produced by Quartz Crystal manufacturers, and has become the most widely accepted Crystal package in OEM production.
A short guide to designating the proper call out depending on the package of the Crystal is as follows:
HC-49U: A Through Hole Quartz Crystal with dimensions approximating 10mmx3.8mm with a pitch of 4.88mm.
Example of Package: http://www.oscilent.com/spec_pages/Crystals/QC-141_142.html
HC-49US: A Through Hole Quartz Crystal with dimension approximating 11mmx5.0mm with a pitch of 4.88mm.
Example of Package: http://www.oscilent.com/spec_pages/Crystals/QC-151.html
HC49USM/HC-49USMD: A Surface Mount Quartz Crystal with dimension approximating 11mmx5.0mm with two pads.
Example of Package: http://www.oscilent.com/spec_pages/SMDCrystals/QC-250.html
A full line of Quartz Crystals is available from Oscilent Corporation via the following link: http://www.oscilent.com/catalog/Category/quartz_crystal.htm
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