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One of the ICs for my design comes in LQFP, TSSOP, QFN and even WLCSP packages. I don't care about the footprint, and the only thing that I want to maximize with the package choice is reliability against physical (PCB drops, bending, vibration) and temperature (-40..+85°C) stress to ensure maximum lifetime for a device.

I understand that this probably depends on the PCB quality, solder and manufacturing process (of PCB and the ICs). All I want to know is a kind of rule of thumb for this kind of choice.

I found this slide from here:

Response to stress: DIP/PLCC, PQFP, TSOP

Which seems to imply that bigger packages are more reliable (use saturation of DIP/PLCC > PQFP > TSOP) in certain cases. But is it really the general guideline? Does it mean that tiny WL-CSP and BGA packaging should be avoided when possible in devices intended to be resistant to physical stress? To me it seems counter-intuitive.

Dampmaskin
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Andriy Makukha
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    I read it more as 'the bigger the pins the more it can withstand mechanical stress'. They act as springs, which you do not have on BGA or QFN. – Oldfart Apr 23 '18 at 13:20
  • While you mention mechanical stress in the text "(PCB drops, bending, vibration)", the image shown here describes moisture-related characteristic and whole linked document seems to focus thermal-induced mechanical stress as the closest match to what you mention in your text (it seems to focus on moisture and assembly routines mostly). So what is your question actually and how is the image related? – Martin Apr 23 '18 at 14:21
  • @Martin, thanks for clarifying that. I found that document by query "IC package reliability" and failed to understand that the chart is only related to moisture :( However, I'd love to see a similar study or assessment related to mechanical (drops, bending, vibration) and thermal stress comparing different packaging types. – Andriy Makukha Apr 23 '18 at 14:52
  • It all depends on the kind of device your are designing. If this is a hobby project then go with common sense - the smaller package the less stress on pins and soldering, not to mention smaller and lighter PCB. However if bending is expected then don't use leadless or 4-sided packages. Go with SSOP and let the leads relieve some stress. If this is industrial project then you are in whole new universe. There is a huge volume of research [like this one](https://pdfs.semanticscholar.org/6fb6/946f04b91e2ba586f1576f790510d8ac0efa.pdf) dedicated to this, most of it not available to general public. – Maple May 07 '18 at 21:22
  • Also the document you linked to shows enormous complexity of the problem. I guess that is the reason you could not find a simple "package xxx is the best" answer. One thing that document shows (as much as I understand it, and I understand very little) is that same packages fare different under different tests. Meaning - you probably have to figure out what's best for your _specific_ requirements by yourself. – Maple May 07 '18 at 21:46

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