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BH1715 light sensor problem

Former Member

Dear Guys,

 

We had some trouble with BH1715FVC (Farnell ID: 1716295).

We have mounted some ten pieces of these ICs, and almost half of them work wrong. It means we cannot communicate with them through the I2C bus. The real reason could not be recongized, but they just doesn't operate. After we change the device to another in the same PCB, usually solve the problem witch means the soundness of the printed board. Do you have any idea? I am wondering if we do something whrong. I solder them by hand at about 320 C... I know it is over the required temperature, but that value subjects to a reflow soldering, if I think well, and when I heat the pins at 320 C, it could mean about 250...280 C inside the package.

 

Also interesting that two devices had been operating properly for a week when once broke down without suffering any physical or electrical (presumably) harm. There were some lightening near the two sensors (some 100 meters)... maybe it could be the problem (could it be?), and it means a totally different situation. First I would like to have some idea about the problem I mentioned upper.

 

Thank you!

Adam

  • 0

    Hi Adam,

     

    The amount of heat transferred through to the device by soldering depends on how long the pins were subjected to 320 degC.

     

    There also must be no connection to the pad on the underside of the PCB is the pcb clear of tracks etc under the part?

     

    Are you taking ESD precautions when handling these devices?

     

    Sorry i do not understand your 2nd paragraph, are you saying that the devices stopped working after a  nearby lightening strike? but were working OK until that point?

     

    Do you get any ouput value from the device or were they completely unresponsive?

     

    Kind Regards

     

    Colin Biddle

     

    Field applications

     

    Rohm Semiconductor

  • 0 in reply to Former Member

    Dear Colin,

     

    First, thank you for your reply! I answer to your thoughts in order.

     

    Depends on the time, of course. What can be a normative about the max soldering time per pin at the temperature mentioned? Maybe I heat them too long.

     

    There is a track under the device, to the DVI pin. Do you think it can effect the operation? If yes why is that when I change the part to another, it works?

     

    How sensitive are these devices are? We take basic ESD precautions, just like in case of all other device we usually use. It means I touch a grounded metal object before I start soldering.

     

    "devices stopped working after a  nearby lightening strike? but were working OK until that point?" Exactily, yes. Do you have idea about this case? It is usual?

     

    For the last question I have to consult with our sofrware developer, after that I will update the topic with that info.

     

    Thank you for your detailed help!

     

    Have a nice day!

     

    Adam