Our team is working on several new electronic devices whose application is primary, flight critical hardware for commercial aircraft.

Our initial component selection includes many QFN packaged devices (leadless, bottom side termination only) which will be mounted on .063" FR4 boards using SN63.  The devices range from 20 to 44 terminations.

From studies that are available on the web, a picture has emerged that QFN packages have reduced long term solder joint reliability when compared with leaded or some of ball grid array devices.  Board thickness, flexing and whether the device has a central solderable heat sink seem to have a significant affect on reliability.  Problem is there are no absolute numbers, so for critical applications it seems that thorough testing is required.  We'd rather not wait until the end of a lengthy test regimen to find we've gone down the wrong path.  Is there newer information abbailable?   Two of the studies stated that further testing was being performed to support the reliability requirements for aerospace and other high-rel applications however I cannot find any updated information on the web.

We have decided to replace several of the QFN's with leaded devices, however there are no direct crosses for 3 of the devices. One of them will require a number of components to create the same function; possibly an additional circuit card.

Is anyone aware of information or recommendations that would be useful for our assessment?  Is there any specific information that would drive us to use or not use them?

Thanks for your help

Gregg






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