September 29, 2022

Another consequence of the shortage of supply: the misadventures of mass production

Chips can suddenly disappear from the supply chain or become very expensive due to the recurring shortage of supply, companies are now designing their PCBs to support multiple chips, either selecting instant replacements or creating multiple footprints to meet at least one alternate room. This means that one PCB and multiple BOMs are needed to be more resilient to any supply disruptions.

Radxa has done this on the ROCK 3A board for the USB PD circuit with the ability to use Injoinic IP2315 or WCH CH224D IC. They are not pin-to-pin compatible chips, and two circuits were designed for the board requiring two BoMs because it is not just possible to replace only IP2315 with CH224D.

But this information did not reach the stock manager, and once the IP2315 was out of stock, he/she thought it would be possible to simply replace the IP2315 with the CH224D. The unlucky part is that the factory didn’t notice/report the incompatibility, and the board still passed QC during mass production using a 5V power adapter, although no voltage greater than 5V could not be negotiated. This led the company to ship Rock 3A boards with the wrong circuits between April 22, 2022 and June 15, 2022, almost 2 months.

Since the card performs well under light loads or with few peripherals attached, it’s quite possible that many users haven’t noticed it. But the card is more prone to random reboots under heavy loads or when multiple devices are connected to the card, which increases power consumption. But wait… How do I know all this? This is because Radxa did the right thing and publicly announced the problem on their forum, apologized to their users, and offered solutions which we will discuss below.

ROCK 3A production batch

You can check the manufacture date of your card on the box as shown above.

Radxa also offers three potential solutions to the problem:

  1. Replace or refund the card concerned via the distributor where the card(s) were purchased
  2. Provide free IP2315 IC for DIY users to repair by themselves (advanced users only)
  3. Provide free 12V/3A USB power adapter

We recently complained about the (damn) 12V USB power adapters that only come with some mini PCs and a Raspberry Pi 4 laptop, but it turns out they may have their uses…

mass production crash IP2315 CH224D
CH224D can be removed and replaced with IP2315

Radxa has also taken steps to prevent such incidents from happening in the future:

  1. Added an ADC voltage test case that requires a voltage greater than 9V to be detected for it to pass QC.
  2. The production must strictly follow the BOM, and for any change of components, the ERP administrator must be notified and provide a new correct BOM.
  3. The factory has been advised that if there is a discrepancy between the BOM and the parts, they need to check with our engineers…

While there have been some mistakes along the way and lessons learned, this particular mass production incident would not have happened without the current supply shortage which has increased the complexity of design, sourcing and manufacturing.

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