LMZM23601: Vout=Vin

Hello

I don't see anything obvious that you are doing wrong.  It almost looks like the FB pin is not connected to the VOUT.

You could try to check continuity between FB and VOUT, even though your PCB snapshot shows a connection.

Also, be sure that the FB pin is soldered correctly.

I will consult with our module group to see if there is anything else to look for.

Thanks

With the module in place, I can't really check the continuity between FB and Vout as the pads aren't accessible under the LMZM. I've tested the continuity on blank PCBs and the pads are connected.

Meanwhile, I reflowed a new module on a new PCB and got the same result. I also removed one of the previous modules and resoldered it - same result. These are the only components on the PCB.

Right now, I have three LMZ23601 modules with Vout=Vin. They were hand soldered, reflowed and twice reflowed, respectively. Two boards were ultrasonically cleaned and the third still has no-clean flux on it.

Should I suspect a bad batch?

Hello

I will talk with our module engineers and decide how to proceed.

I will get back to you before the end of this week.

Thanks

Hello

Can you tell us what your soldering temperature profile is ??

What is the maximum soldering temperature ?

Thanks

The maximum soldering temperature is 232º.

Preheat to 125º for 180s

Soak at 175º for 120s

Ramp up to 232º in 140s

Dwell at 232º for 40s

Cool down at less than 3º/s

Hello

Thank you.

I will talk with the module team and get back to you as soon as possible.

Thanks

Hello

I have some comments and questions from our module and package team:

1. Where is the device failing initially (e.g. production testing, reliability testing, or field)

2. Is this a new application or is this application running in volume and since when?

3. Can you please provide a copy/photo of the TI label of the reel where the devices came from.

4. This module is rated MSL3-260°C. The peak temp of 232°C seems to be a little low. It is hard to comment on the reflow by description without a plot.

5. Below are some key parameters of a recommended reflow profile:

Pre-heat/soaking 150°-200°C     60-120 sec

Reflow time >217°C             60-150 sec

Ramp up                       <3C/sec

Cool down                     <-6C/sec

Peak temp                     240°-245°C

Duration within 5°C to peak    less than 30 sec

6. Please return your failed boards, according to the below procedure.

For the customer return process please do NOT remove the units from the board as we would like to preserve the failure and not impact and change the failure mode by the desoldering  and handling. However,  at TI we have to destroy the board in order to access the device, pls confirm that you are ok with this process.

For products purchased directly from TI or the TI store please follow this return request procedure:

1. Request analysis of suspected nonconforming product using the return request submission form.  Be sure to include picture of the top of the unit (with TI symbol) in the submission form attachment
2. Upon TI acceptance of the request, return instructions will be provided. Please do not ship products until instructed with a CPR\QEM number.
3. Follow TI's guidelines for handling customer returns.

For products not purchased directly from TI or for additional information regarding TI customer return policy, please see  http://www.ti.com/support-quality/resources/customer-returns.html

Thanks

Hi,

The device is failing at production testing for a new application.

We are redesigning the power supply module of our application to improve efficiency. The LMZM module is replacing an LDO.

These failed units all came from samples requested through TI (sales order T00927166) - unfortunately I no longer have the antistatic bag with the reel information.

The reflow profile I'm using, apart from the peak temperature, seems to agree with the suggested reflow profile. Ramp up is <1ºC/sec, and time >217ºC is > 60s.

I'm OK with sending a board for inspection. 

Hello

Thank you.

Please use the above instructions to send the failed boards to TI.

Thanks

Hi,

 I already submitted my return request. I'm waiting for an answer.

Thank you for the help.

Thank you Afonso for the update.

Regards, 

Denislav