MSI Blames Faulty Heatsink For DOA Z790 Motherboards, Offers A Fix

Closeup of the heatsinks on MSI's Mag Z790 Tomahawk WiFi motherboard.
Is there anything worse than piecing together your PC build, pressing the power button, and then...nothing happens? Well yes, there are a myriad of things worse than a non-booting PC. But it's still highly frustrating, and also potentially stressful, especially if the root cause isn't immediately obvious. It's also what some owners of certain MSI-brand Z790 motherboards have been contending with over the past several months. Fortunately, MSI finally acknowledged the issue and is working with customers to replace their busted boards.

MSI's acknowledgement follows a recent video posted to the YouTube channel Joshi Repair, which is a repair shop based in the UK. In the video, repair technician Abdulla Joshi removes the heatsink from the chipset on MSI's MAG Z790 Tomahawk WiFi motherboard. After cleaning off the thermal goop, several hairline cracks and scratches become strikingly visible.

He also shows the cracks under a thermal camera, which reveals the extent of the physical damage of the platform controller hub (PCH) chip. Here's the video...

Cracks on a chip's die are never a good thing. And in this particular case, there are safeguards put into place to prevent this from happening—Joshi comments that MSI's "quality control is fantastic," noting that it's "one of the few companies that actually sends their PCBs, every single one, through a specific machine that takes a very high photo of the PCB itself."

If that's the case, then how did multiple motherboards with cracked PCH chips sneak through to retail? In the video's comment section and also on Reddit, MSI explained the culprit. Here's MSI's statement...
"Regarding the MAG Z790 Tomahawk WiFi incident, we've discovered that a minority of units may encounter non-functional PCH potentially resulting in Dead on Arrival (DOA) of the motherboard product. We have isolated the cause to a previously used chipset heatsink screw design and have taken proactive measures to address this issue.

A revised chipset heatsink screw design has been implemented into our production, and the known cases have been resolved.

We uphold high standards of responsibility and accountability, and want to assure affected customers can promptly receive product replacements. Please contact our local customer service center for assistance."
From our reading, it sounds like the "screw design" was over-tightening the heatsink, to the extreme point of causing physical damage. This would explain why MSI's camera images of the PCH would not ring any alarm bells, because they're presumably taken before the heatsink is applied, versus applying the heatsink, removing it, snapping photos, and then reapplying.

It's not clear exactly how many units are affected by this defect. However, there's at least one report from nine months ago from a user on Reddit who received a damaged board, returned it to Newegg for a replacement, and received another damaged board. That user ended up switching to an ASUS model (hopefully not the $700 model with a typo).

Additionally, MSI stated in a follow-up comment that if a board was working for awhile before giving up the ghost, then it's not impacted by this issue. Still, if you own a Z790 Tomahawk WiFi and it suddenly dies, we recommend checking the PCH just to make sure—it's not out of the realm of possibility that the stress from an over-tightened heatsink could lead to cracking after the fact.