EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: ApexM0Eng on July 13, 2015, 10:36:59 pm
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Such as devices like the one below.
http://www.qt-brightek.com/datasheet/QBASS40YGZ.pdf (http://www.qt-brightek.com/datasheet/QBASS40YGZ.pdf)
If you check out Page [5 of 10] you can see a diagram of the device.
Pins 6-8 and 9-11 are all mounted underneath.
I had a small board made up using the recommended pattern in this document.
I have tried using solder paste, by placing very small dabs on the pads then heating,
but I am always getting shorts between the inside and outside pins.
I really don't like the clearance between the inside pins and outside pins on the recommended
layout, but i figured it was fine.
Whats worse is I can't get in there to fix mistakes as the device is now glued down.
Is there a technique i am un-aware of or something? This is quite frustrating.
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Ideally, a paste stencil.
It can be hard, but not impossible to get sufficiently little paste with other methods.
A pin or toothpick can work sometimes.
And of course a PCB with solder resist.
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Looking at the PDF I see holes going through the display substrate. I'd use short wires and solder them from the top of the display and the bottom of the PCB.
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What I do in these circumstances -
Elongate the pads with a larger pad close by. Drop a 35-50th hole in this second pad. Apply flux to the pads, place and tag the display.
Using thin solder and a thin tip, heat the pad/hole and run solder down the hole. It will flow all over and pick up the display pads.
The PCB should be upside-down for gravity assist.
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So small dabs, we are talking like .5 cubic mm, when fitting on the end of a pin.
I was thinking about using a fine syringe to place some in the hole on the device then heating the contact pad on the top, but I am concerned that
if it isn't pressed firmly down that the PCB won't conduct the heat properly.