QFN solder mask

Discussion in 'General Electronics Chat' started by adrenalina, Sep 9, 2015.

  1. adrenalina

    Thread Starter Active Member

    Jan 4, 2011
    78
    3
    Hello everyone. I've had a couple of boards made that have .5mm pitch QFNs, and I noticed that some boards have the solder mask over the pads, although some have the solder mask pretty well aligned. I am attaching some images so that you can see for yourself.

    Anyway My question is, is it better to increase the soldermask expansion on these chips so that there is no mask between the pads or to risk having mask over the pads? Currently I am using a mask expansion of 1mil.
     
  2. Jure Petric

    New Member

    Sep 9, 2015
    6
    1
    I think it's bether to risk over-pad mask becose you can still simply remove it with sharp object. If you will solder QFN by your self you'll be glad that the mask is between pads because you'll avoid short circuit.
    If you'll do it with overflow owen and solder paste and serial i think is bether second option (withoud mask).

    QFN-s are pain in the a** if you solder them manualy with hot air :D

    I wish you good luck!

    Ou look for another PCB manufactor. I asume that these PCB-s are made in china for very low price?
     
  3. adrenalina

    Thread Starter Active Member

    Jan 4, 2011
    78
    3
    I solder the pcbs with a reflow oven and only hand solder when I have to rework a board. Indeed, the pcbs are made in china, Overall the quality is pretty good for the price. This is the only problem I have encountered with small pitch devices.

    I have soldered about 100 of these boards, and just noticed this problem when reworking a board. The only problems I have had is that some pins were not correctly soldered. I assumed that this problem could've been caused by the solder mask over the pads.

    That is why I am asking if its better to not have solder mask between the pads if solder with reflow oven and only solder by hand when a board has to be reworked.
     
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,769
    969
    Absolutely leave the solder mask between the pads and find another PCB vendor.

    Not sure who you used but with low volumes/proto quantities I've had VERY good luck with the board house that itead PCB uses..
    http://imall.itead.cc/open-pcb/pcb-prototyping.html
    Pricing and quality so far for me is excellent.. (I've done multiple 4 layer and double sided boards with them and components down to 0402/.65mm DFN without any problems)
    Just my 5th board from them today and 1 more coming next week.. ZERO problems on any of them.
     
    cmartinez likes this.
  5. adrenalina

    Thread Starter Active Member

    Jan 4, 2011
    78
    3
    I am using http://www.elecrow.com/services-c-73.html
    I like that I can get a stencil for all of the boards that I send out for 16 dollars, which I have not found anywhere else.

    Does itead have shipping with dhl? Do you know how much it costs?
     
  6. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,769
    969
    Yes and air mail,etc...
    http://imall.itead.cc/shipping_and_returns

    I just ordered 10pcs of up to 5cm x 5cm and shipping cost me $4.50 for registered air mail to me in the US.. Order total was $15
    So $1.50 per board shipped.. Can't beat that anywere IMO..
    But that was registered air mail.. DHL is higher cost if thats the only service you can get where you are..
     
Loading...