The quartz industry has a reputation for poor quality. Some of it is because it is difficult to maintain consistency in quartz production. However, part of it is self inflicted by the way quartz companies resell and relabel their product.
Because there are so many combinations of frequency, package, supply voltage, and various other specifications, there are thousands of “standard” quartz resonators. Far too many to keep in stock or tool-up to build. So the quartz industry has developed a resale-and-swap model where many, and in some cases most of the product a supplier may “manufacture” is actually bought from partners or even competitors. This is how many quartz suppliers offer a wide range of product – they re-label parts from manufacturers.
In general re-labeling is fine and does not cause problems as long as the manufacturers are high quality and the relationships are durable and consistent. But in this case the agreements are often ad-hoc and temporary. They are often short term buy-sell deals rather than corporate relationships and there is often a lack of quality control. Problem is that the customers think they are buying well qualified and stable product. But really the parts are coming from wide ranges of unqualified manufacturers. And because the ceramic quartz packages tend to look the same (there are only a few package manufacturers) the suppliers can change manufacturers. They can and do even change manufacturers in the middle of their customer’s production runs.
Granted the high quality suppliers don’t do this, but many others do. And chances are you may be buying untraceable product. If your supplier changes manufacturers or the manufacturers change their process then the parts you buy might not work as you expect. Specifically, they may not work like the ones you qualified.They may shift in production; they may fail in your application circuit. How does quartz fail? Main problem is latent startup issues. They may work well enough in your factory, but when they are cold or hot they may not start. Scary? You bet!
Learn more about quartz crystals oscillators