Precise Time Domain Reflectometry (TDR) for Packaging Issues
In a packaged part analysis it is vital to consider that the fail mechanism, namely an electrical open in some cases, might reside in the package as well as the die. Beyond the module itself, the board upon which the module is mounted may have an issue which causes the die to improperly function.
The quickest solution to determining where opens or other anomalies may lie along an electrical path is through time domain reflectometry (TDR). Sage Analytical Laboratories TDR tool can give a high accuracy, fast reading of how far down a conducting path the anomaly lays whether the problem exists in a flip chip, package on package, or through-silicon via device.
Time domain reflectometry works by injecting a high frequency signal into a conducting path, and measuring the reflections. Not only can this show shortened paths, but it can also map the material interfaces of different components along the path. This can highlight paths that have higher resistances or poor connections as well.
By comparing a failing pin result to a control sample’s, we are able to get an accurate gauge of whether or not any package deconstruction is necessary using time domain reflectometry. This leads to tremendous time savings where an analysis could take days, this methodology can reduce it to minutes. Additionally, it prevents some analyses that may have otherwise removed the packaging material to only find a good looking die. Lastly, it can identify weak connections that may lead to future faults.
Sage Analytical Laboratories uses high frequency precision oscilloscopes to measure functional devices. Inputs and outputs of functioning die may be read directly from boards or pins. By observing these signals directly with time domain reflectometry, we are able to do quick bench-top verification of fail mode replication in a nondestructive fashion, or just monitor signals as they are modulated.