The relationship and difference of HC-49S HC-49U HC-49SMD in quartz crystal package

First of all, HC-49S, HC-49U, HC-49SMD are the packaging category of quartz crystal, passive crystal series, is now a few products that are widely used in quartz crystal, because of its low cost, precision stability and other in line with civilian electronic equipment, so it is liked by the factory. The piezoelectric properties of the crystal (silica) chip material can convert electrical and mechanical energy into each other to produce a stable frequency. HC-49S belongs to in-line quartz crystal oscillator package, in-line 2-pin, high shell volume is 10.5*4.5*3.5MM Low shell volume 10.5*5*.0*2.5MM is an international standard, common parameters standard load capacitance is 20PF (12PF 16PF 30PF, etc.) accuracy is ±20ppm. ±50ppm resistance 120Ω, the parameter standard is no different from HC-49U 49SMD. There is also a package called HC-49US. 

HC-49U is also a direct-insert 2-pin crystal , the volume is 11*4.5*13.4mm, and the functional application is almost no difference with HC-49S, because the volume is larger than 49S, resulting in a waste of circuit board space and high cost has been gradually replaced by HC-49S package. It should be noted that HC-49U is different from HC-49US, and HC-49US refers to HC-49S rather than 49U.

HC-49SMD, commonly known as "fake chip type", this is a patch type 2-pin crystal except for the pin, other parameters are the same as HC-49S, 1 volume 10.5*4.5*3.5MM, specifically HC-49SMD is processed by flattening HC-49S foot - set on the gas-shear foot - braid and other production processes. Due to the increase of materials and processing costs, it will be more expensive than HC-49S, and the common frequency points are 8MHZ 12MHZ 11.0592M 13.560MHZ