dye and pry test

DYE AND PRY TEST SERVICE

D

ye and pry testing (also called "dye penetrant test") reveals hidden discontinuities beneath SMT components. Although destructive, dye and pry test is the most efficient and cost-effective means of examining 100% solder connections of BGA and other bottom-terminated SMT packages. It can also be used to confirm cracks or leaks on sealed SMT parts. 

How it works

Sample preparation begins much like a cross-section. The area of the board area containing the target component must first be excised from the rest of the board, using a specialized diamond saw blade. It is crucial to use the proper equipment and technique here, to avoid introducing vibration or shear forces that could compromise the integrity of the sample and create new defects.

Next the sample is immersed into a low viscosity red dye, inside a vacuum chamber. Capillary action pulls the liquid dye into every crevice and void, assisted by the pressure differential created by the vacuum. After dye immersion, the sample is baked dry in a moisture removal oven, then carefully fixtured in a puller assembly to separate the component from the board. Board and component are then examined under a microscope, where defects and anomalies are recorded and imaged.

 

Dye & Pry or Microsection?

Both methods are useful tools for process validation and failure analysis of bottom terminated components, but which is suited for your project? Of course, it's often advisable to begin with X-ray, CT X-ray, and/or visual microscopy while the sample is still intact. Assuming destructive analysis is still indicated, is this a root cause investigation, or do you simply need to validate a process? If failure analysis, have you already pinpointed the location of the suspect circuit and/or pins? How many samples can you afford to destroy, and what is the project budget? Here's a helpful summary to position the methods:

 Dye and Pry

 Microsection

Lower cost per joint

Modest amount sample prep time    

Better suited for process validation than root cause FA

Look at 100% solder connections at once

Limited data ("yes or no" opens, see horizontal point of separation)

Higher cost

Lengthy sample prep time, potting and multi-step polishing process

Excellent for root cause FA, but must select the right target plane for section, or else section all rows

Look at one row of solder connections per cross-section

Detailed data (intermetallic layers, fracture propagation path, voiding, grain structure, solder wetting angles)

 

For help with your investigation, contact the solder experts at Process Sciences.

Microsection | Cross Section | BGA Analysis