You would think all memory assemblers would test every module they build.
Some assemblers test only a sample of parts and call the entire lot good based on an "acceptable defect level." These companies argue that it's cheaper to get a certain amount of returns than to detect and/or prevent them. This may be true for their bottom lines, but if you're in the small percentage of end users that ends up with a failed part, you probably won't think it was a good idea. At Micron, we test each and every memory module we manufacture.
There are several different methods used to assess memory modules. Many of them take modules through a series of tests, including checking for opens and shorts, leakage, verifying refresh rates and running pattern tests. All of these tests are typically performed at high speed to ensure functionality.
As an additional safeguard, many assemblers have invested in automatic handlers to manage their modules. This prevents an operator from accidentally placing a failing module into a good tray. The yield at this step should be greater than 99%.
On top of these production tests, reputable assemblers will also pull additional samples for outgoing quality checks and to qualify the modules on different motherboards. As processors and memory speeds become faster and faster, it becomes increasingly critical for memory modules to do more than just meet standard specifications. They must also be proven to work in specific systems.
Unfortunately, many assemblers consider comprehensive testing an unwarranted expense. Some of the equipment is extremely expensive and requires a great deal of engineering support. On the other hand, it can be very easy for an assembler to buy an inexpensive hand held tester, just to check for opens and shorts and perform no additional testing.
Symptoms of Bad Memory »