Hi Everyone, I'm a beginner level Hardware Design Engineer. Recently one of my clients has been experiencing a SIM Card damage issue when the SIM is used in the board for a long period of time (Like 2-3 months). I am not able to understand why this is happening. We have been using the same circuit for couple of years but haven't encountered such a problem. For security reasons, I cannot share the circuit here. The circuit is pretty standard. Has Power, Data, clock, RST, GND and SIM presence pins. Each of the digital signals have a series resistance of 27R and 33pf caps in parallel. The power signal has 1uF cap in parallel. The data line has been pulled-up to SIM VCC (power). There are ESD diodes in parallel as well. Could anybody help me understand this?

 

Hi jk,
Please define what type of SIM card damage, electrical/mechanical/contacts.??

E

 

Although the client was not very specific, the damage is mainly with the proper functioning of the SIM card. The SIM is no longer detected and read by the host processor. Therefore, the host processor is not able to fetch data from the Card

 

hi jk,
I guess you have tried reading the faulty SIM' s on your in-house system?
In order to check that it is not the clients' hardware/system
E

 

Yes. The SIM cards with us have been functioning properly on our Evaluation boards (till now) but we suspect some issues with Client's PCB. The SIM cards used to work properly but seems like they are getting damaged over time. Does some PCB design issue lead to this problem?

 

Are the SIM cards definitely from a reputable source?

 

Due to your “security” concerns, and general vagueness any answer you get will be so speculative that it has a lottery ticket’s chance of being correct.

Your only hope is that someone has—by chance—experienced a similar problem and happens to see this, and choose to answer. Otherwise, what will now follow is a game of 2⁸ questions ending in you either vanishing and leaving the thread unresolved or telling us “problem solved” while being unable to give any details due to “security” concerns.

In a case like this, as a business that is making money from the circuit involved, it is really the proper route to hire a consulting engineer, have them sign an NDA, and give them all of the details you “can’t“ give us.

Your (management’s) unwillingness to spend money on expert help puts you in a no win position. Good luck in any case.

 

Over voltage would be the most likely cause.

Is board power supply provided by you or the customer? Could he be giving it too high a voltage?

 

Is your customer removing and replacing the sim and damaging it inadverently with ESD?

 

Silly question, but what is a SIM card besides the one that is plugged into a cellphone?

 

Due to your “security” concerns.................

Hi Ya'akov. Hahaha, you are definitely right here. Thank you for being very honest. I do agree, this is sort of trying my luck here. Very few people have worked on SIM card validation in particular. But I just hope there would be somebody out there who has encountered a similar situation. But if I ever get the answer I promise I'll update here as it might help somebody else as well. I'm so thankful for everyone who has contributed at least some of their valuable knowledge. At least we are learning something from somebody else everyday. I am attaching a rough sketch of the circuit as well. Have a great day

 

Is your customer removing and replacing the sim and damaging it inadverently with ESD?

That could be possible

 

Silly question, but what is a SIM card besides the one that is plugged into a cellphone?

Cellular Modems

 

Cellular Modems

Thanks. Why does the user need to remove the SIM card?