PCB Failure Analysis using Dye Penetrant Techniques
The study of PCB failure scenarios that involve the search for an open circuit is one of the most difficult cases. Time-consuming and frustratingly frequently fruitless, using probes and an ohmmeter to navigate the maze of metal interconnects is required when an analyst comes across a ball-grid array (BGA) with hidden connections that preclude further probing. The analyst is now in a difficult situation because desoldering the component will eliminate any traces of an open circuit and doing a blind cross section is risky unless the component has a significant number of open solder joints. In these situations, dye penetrant testing can be utilised to find any solder flaws, exposing cracked or unwetted junctions at the expense of further testability.
A failed circuit board is immersed in a vivid dye as part of the dye penetrant technique, also known as Dye and Pry. The sample is then subjected to alternating vacuum and pressure to drive the dye into any cracked or incorrectly formed solder connections. After the sample is removed from the dye and allowed to dry, any questionable components are hastily (but carefully) torn off the board, exposing the connection surfaces. The interconnecting surface is examined from both the component-side and the board-side for any traces of dye; the presence of dye on any surface where a connection is intended to be formed is a sign of an open circuit. The sheer number of surfaces that need to be examined makes the inspection time-consuming, so the type of dye used must be carefully selected with attention given to both its visibility and material properties like viscosity. Infinita lab uses a deep crimson dye that is not only easy to see under a microscope but also very fashionable in the inevitable event that an analyst spills dye on themselves.
Although dye penetrant testing is helpful for analysing PCB failures and unintentionally spicing up outfits, it may also be used to test other kinds of devices with equal success. Hermetically sealed packages can be checked with the dye to see if a good seal has been obtained; conventional plastic-encapsulated devices can also be tested to see if and how much delamination is spreading from a package’s edges, possibly in place of (or in addition to) acoustic microscopy. Dye penetrant can even show incorrect wire bonding when applied in this way, especially over the leadframe!
Read more: PCB Failure Analysis – Dealing with Burnt and Mangled Boards
While helpful, dye penetrant is only one of many methods available to analysts for PCB failure investigation, and it is not always the best option. Dye and pry testing cannot be done when additional electrical testing is sought since it is inherently destructive; in addition, if contamination is suspected, the dye would effectively hide any potential residues that might be the problem’s primary cause. So, it is essential to have an analytical team with experience look over the project before deciding whether dye penetrant testing is necessary.
