Electricity path: Car battery → entering device main PCB → FFC cable → 3.3V regulator on sub PCB → FPCA cable → This transistor on FPCA cable
However, we never found any problem with this transistor before, this is the first case. So, my supplier is not willing to conduct any countermeasures to prevent this issue.
Has anyone found yourself in this kind of situation and how do you explain to customer for a closure?
This is always a difficult situation. How do you tell your customer that your supplier won’t do a corrective action. I recommend seeing if there is anything you can do to provide the customer some kind of corrective action. You may want to review the industry council whitepaper on EOS which gives a great fishbone diagram for all kinds of EOS root causes. It can be downloaded at Industry Council White Paper 4: Understanding Electrical Overstress | EOS/ESD Association, Inc.. If you find a root cause that seems to fit the situation, like hot plugging, you could see if there are any instructions to the customer you could update, like make sure the cable is de-energized and grounded prior to plugging it in. If there is nothing else you can do without the supplier’s support you could also say this is a first-time occurrence and you will continue to monitor for additional failures. Perhaps the customer will take this answer. If not, you may need to use an independent lab to do the failure analysis. Thanks
I agree with Andy, this is a sticky situation and he has given a good path forward.
Additionally, I would suggest getting with your contracts people and review the statement of work and any quality clauses you may have flowed to your supplier. Typically, there is some sort of statement about suppling defect free components. You may have a contract path you can go down to have your supplier perform the cause analysis .
unfortunately, even 9 years after the release of White Paper 4 referenced by AndyN, there is still a lot of confusion as the term “EOS” is concerned. To overcome this confusion, it was clarified in White Paper 4 that EOS is a violation of the absolute maximum ratings (AMR) of a device, whereas the term “EIPD” (electrically induced physical damage) was introduced as a compromise to denote a damage caused by electrical stress.
So, when you are referring to “EOS” have you already verified that the AMR were indeed exceeded or do you use this term instead of “EIPD” just to denote an electrical damage? I am asking because the former implies already quite some root cause analysis effort, while the latter does not.
To complement the process suggested by AndyN you can also narrow down the stress type that had cause EIPD, by determining the electrical characteristics of the damaged structure (e.g. its breakdown voltage) and narrow down the dissipated energy by means of a power-to-failure analysis. An example of the latter is included in chapter 5 section 5.6 of White Paper 4.
In addition, to narrow down the root cause you need as much information as possible from your customer on the conditions that caused the failure. When was the device last known to be good? When was it found first to be damaged? What happened inbetween?
Finally, after White Paper 4 was released a standard practice was worked out to help Tiers and OEMs to deal with EOS (suspected) failures more efficiently:
“ESDA, USCAR LLC, ANSI/ESD S27.1-2018: For the Recommended Information Flow for Potential EOS Issues between Automotive OEM, Tier 1, and Semiconductor Manufacturers, 2018”
This document may also help you to get your customer “on the same page”.
Thank you so much Andy. I already read the paper and tried to conclude all possibilities and reported to customer. I hope they can help me to find the cause.
Thank you for pointing out, I understand about the difference between EOS and EIPD. However, I mentioned EOS damage as my overseas supplier stated. Unfortunately, they are not willing to share their specification and conduct any simulations. I will talk to them about this.
Moreover, appreciate your recommendation about the ESD S.27.1, I will review it.
Thank you so much again for your generous sharing!!
