• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Subscribers 65 subscribers
  • Views 1864 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMZ23610 shorts after soldering and wrong voltage

Martin Kull
Prodigy 20 points
Other Parts Discussed in Thread: LMZ23610

Hi all,

we use the LMZ23610 in several different boards with output voltages from 1.2V to 5V. After soldering (vapour phase, 2 different furnaces), some of the LMZ parts have shorts at the output and sometimes at the input, too. If I apply an input voltage, most of them work and the short disappears. At some parts the short does not disappear. Other parts have a wrong output voltage - the feed back voltage is not 0.8V in such a case. Some parts are too low (FB voltage is 0.5V, for example) others are too high. We bought these parts at Farnell in June 2014. At the moment I have 5 parts (of 20) with problems. We have approx. 7 years experience with the vapour phase systems and all other PCBs - even if soldered twice (top bottom) do not show problems. So I assume that this should not be the reason for our problem.

The schematic is more or less a copy of the datasheet (FB resistors, capacitors,...), we have 2x330uF output capacitors + 22uF + 47nF ceramic, etc.

Is there a known problem (soldering, bad parts delivered in June,...)

Does anybody has an idea?


Thanks

Martin

  • 0
    TI__Mastermind 28020 points

    Hi Martin,

    Is this the first time you are using these devices? Have you soldered these successfully in the past?

    Is it possible to send your schematic and vapour phase temperature reflow prolfile to me directly at jarrigo@ti.com?

    Thanks, Jason

  • 0 in reply to J Arrigo
    Prodigy 20 points
    Hi there,

    I have had the same problem as Martin, only slightly worse - a 50% failure rate. After the reflow process 5 out of 10 of the PCB's had the LMZ23610 with the same failure mode. The failure was that the input was being shorted to ground, and the output had a resistance of about 7 Ohms to ground. Was Martin's problem ever resolved? I was wondering if the outcome might shed some light on my problem, as it sounds very similar. A previous manufacturer had a 100% success rate with these devices on the same PCB design, but we only had 2 made so it's not much of a statistical comparison! Any help appreciated :)
  • 0 in reply to Leigh Harvey
    Prodigy 20 points

    Hello Leigh,

    Jason sent me a soldering application note for these devices. We assume that there is a problem with moisture. At later shipments of these parts I better checked the packaging at arrival (the sealed plastic bag) and found little damages from transportation or from handling in the stock at our supplier. The moisture indicators always have been ok, but you never know when they have packed new ones into the bag...

    Now I baked the parts and still had one or two failures of approx. 20 parts. I think they are really at the limit for lead free soldering. I like the parts as they are easy to use and have good performance. Another supplier of very similar parts told me that they do not guarantee function after vapour phase soldering.

    In the next weeks we'll get a ultra low humidty storage cabinet and I hope that the failure rate will go close to 0, then.

    Best regards


    Martin

  • 0 in reply to Martin Kull
    Prodigy 20 points
    Hi Martin,

    Thank you very much for your reply!

    That's interesting and useful information - I am checking now with our new manufacturer exactly what reflow profile they used to determine whether the recommended profile was used. I have a suspicion you might be right about them being close to the limit for vapour phase soldering - the datasheet revision history indicates they might have been considering this, as the changelog on page 28 (of the Oct2003 revision) shows the addition of a peak reflow case temperature of 245degC...

    Thank you also for the advice regarding baking the parts - I will suggest this to our manufacturer for the next batch we have made. If I learn anything further that may help you I will post back here with an update. I agree they are impressive and compact devices, so I am loath to ditch them on our design if I can nail the manufacturing issues.

    Thanks again and Kind Regards,

    Leigh
  • 0 in reply to Leigh Harvey
    Prodigy 10 points
    Dear all,

    we have similar problem: we shifted to LMZ23610 on our boards. After soldering 50% of the PCBs are not operating due to failing LMZ23610. Many do not give any output voltage, some a wrong output voltage. Only 50% of PCBs are working well.
    Is there any sustainable solution?
    Could you advice some "easy-care" 24V input to 5V/10A output DCDCs?
    (then we might redesign the PCBs)

    Many thanks
    Mike
  • 0 in reply to J Arrigo
    Prodigy 20 points

    hi,Jason

    the part of LMZ231610TZE I used,when i make this part work continuously 4 hours at 67°C,the input  was always shorted to the output ,i don't know why.