I'm just looking for some extra resources for thermal impedances of JEDEC standardized packages. I've already found one such article posted by JRC, https://www.njr.com/semicon/package/thermal.html , and another by LT, https://www.analog.com/media/en/package-pcb-resources/package/thermal-table.pdf. I was just wondering if there was another resource for typical thermal impedance values for commonly used packages that anyone on here uses. I also attempted to search on the JEDEC website to see if the parameters for packages included typical thermal impedances but for some reason I couldn't even find the JESD30G document that is supposed to contain all of package information. Any help would be appreciated. I'm planning on using this for ICs where the thermal impedance is not listed in the datasheet or online, but it does contain package information so for now I am just trying to compile information.

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    \$\begingroup\$ These tables only give rough estimates...I'm not sure how useful that would be. Can you give an example of a device where the manufacturer does not provide thermal information? \$\endgroup\$ – Elliot Alderson Jul 1 at 14:59
  • \$\begingroup\$ You want examples? Is it not good enough to take my word for it that the datasheets I'm looking at haven't provided adequate information? \$\endgroup\$ – Cooper Woodward Jul 1 at 15:06
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    \$\begingroup\$ This will just increase your frustration, but JEDEC doesn't dictate what happens inside the package -- so depending on any "typical" number is going to come with some danger. I'd fall back on the rule that if it's not in the datasheet then that's an indication that the manufacturer doesn't care or is embarrassed by it, and you should buy a different part if it's at all possible. \$\endgroup\$ – TimWescott Jul 1 at 15:49
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    \$\begingroup\$ Pretty please, I'm just curious, it's not an assault on your credibility, I just want to see which manufacturers are not providing the important information. Please with sprinkles on top, just one link to a datasheet? This isn't the reference desk, this is a community. \$\endgroup\$ – Elliot Alderson Jul 1 at 16:24
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    \$\begingroup\$ @CooperWoodward yes. You can put anything that's small enough into a package, so it makes all the world of a difference how your manufacturer thermally connects the IC to its package. Thus, all chips where it matters pretty much must specify that in the data sheet. If it's not specified in the data sheet, the manufacturer (most probably intentionally, since this is so easy to measure) makes no guarantees, and thus, no "typical" values would help you in any way. So, bring forth an example! \$\endgroup\$ – Marcus Müller Jul 1 at 16:25

The black plastic has Rthermal about 100X that of copper or silicon.

In many packages the plastic distance, between silicon die and the various metal leads, sets the total thermal resistance.

The manufacturer can pick various CAVITY sizes; large cavities and small die will have long bond wires (more gold cost, and more thermal resistance at 10,000 degree Cent per watt), and will require lots of plastic between sides of the silicon die and the pins.

For lowest thermal resistance, you must XRAY the product and ensure the die almost totally fills the cavity.

So if you really care about 150 degree C per watt, versus 200 degree C per watt, you need to write a specification directed to the IC packaging engineer (inhouse, or a contract house) and probably have an INSPECTOR on the assembly line, to ensure your ICs use the package with the cavity that fits snugly (a few mils larger) around the die.


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