What are the Best Practices and Tests to Ensure Strain Gage Longevity?

A customer recently asked the following question:

We are using the M-Bond 610, and following your guidelines for this adhesive.  The strain gages that we’ve bonded appear to work well, other than visual inspections and calibrating the pressure sensor, is there any testing that we can do in order to verify that our bonds are good and will last 20+ years?  Is there testing that you can do?  Or do you have any recommendations on testing we can do to insure our bonds between the pressure sensing element and strain gage will meet the long life requirements of the product? 

Recommended Check List:

1. Consistent manufacturing practices (checked periodically to confirm).

2. Cure (ramp rate and final bond line temperature/Time)

3. Close visual inspection. Looking for voids or other indication of inconsistent clamping, or cracking of the foil/backing.

4. Post Cure (50° F above cure temperature for at least 2 hours)

5. Prior to doing circuit refinements, proof load 3 times to at least 150% of Full Scale (Any micro-yielding of the spring element will occur). Any marginally bonded gages will likely fail.

6. After wiring be sure flux is thoroughly removed (10K megaohms or higher resistance to ground). Residual flux can cause the transducer to drift and or be unstable.

7. Prior to applying protective coating, one can bake out volatiles and moisture by conditioning the load cell in an oven at the highest temperature compatible with the materials used.

8. Ensure that the proper environmental protection is applied.

9. Purge with an inert gas and hermetically seal.