I am thinking about making my own FPGA board and soldering using reflow. The tutorials I've read all say the process requires temperatures in excess of 220 °F. However, at least according to this datasheet, FPGAs have "max operating temperatures" below 200 °F. How does one then solder an FPGA?

EDIT: I have a new question in response to the answer given. Why would the max operating temperature differ from the max soldering temperature?

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    \$\begingroup\$ You don't try to operate it while soldering it. A different part of the datasheet specifies the allowable soldering temperature profile. \$\endgroup\$ – Dave Tweed Aug 9 '14 at 1:35

Soldering temperatures are normally in excess of 200°C (400°F).

The soldering guidelines for Xilinx Pb-free packages are here. Usually lead-free soldering requires somewhat higher temperatures than eutectic Sn63-Pb37 solder.

It's not a problem to have brief exposure to soldering temperature of 220°C or even higher.

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The max operating junction temperature is the maximum temperature of the IC die with voltage applied (typically 125°C for an FPGA). High current densities on a chip combined with high temperatures eventually can cause failure due to metal migration.

The outside would have to be much cooler than that. The maximum storage temperature is the long-term maximum temperature with no voltage applied (typically 150°C for an FPGA). High continuous temperatures can degrade the package or cause impurities to diffuse in the chip.

Soldering is a short-term one-time (or occasional, at most) exposure (measured in seconds), so the damage caused, for example, by diffusion of impurities, is limited.

  • \$\begingroup\$ Why does the max op temp differ from the max soldering temp? \$\endgroup\$ – Elliot Gorokhovsky Aug 9 '14 at 1:56
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    \$\begingroup\$ Please see edit. \$\endgroup\$ – Spehro Pefhany Aug 9 '14 at 2:21

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