How the heck do you solder SMD's that have pads underneath?
How the heck do you solder SMD's that have pads underneath?
(OP)
Such as devices like the one below.
Link
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.
Link
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.





RE: How the heck do you solder SMD's that have pads underneath?
Otherwise, I'd layout those hidden pads under the display so they projected towards the part center a little to allow too much solder somewhere to flow two rather than just beading up and overflowing onto the outer pads.
Also, "then heating" isn't a prescription for success. Are you running a proper drying, pre-heating, reflow, cool down, temp controlled cycle or not?
Keith Cress
kcress - http://www.flaminsystems.com
RE: How the heck do you solder SMD's that have pads underneath?
Dan - Owner
http://www.Hi-TecDesigns.com
RE: How the heck do you solder SMD's that have pads underneath?
RE: How the heck do you solder SMD's that have pads underneath?
If your "very small dabs" are causing shorts then they aren't "small enough"
RE: How the heck do you solder SMD's that have pads underneath?
The gun will melt the plastic on the device, but I have a tip that is fine enough to fit in the hole on those inside pins.
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.
RE: How the heck do you solder SMD's that have pads underneath?
Alternatively take it to an assembler and pay them $20 to put them on.
Keith Cress
kcress - http://www.flaminsystems.com
RE: How the heck do you solder SMD's that have pads underneath?
RE: How the heck do you solder SMD's that have pads underneath?
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RE: How the heck do you solder SMD's that have pads underneath?
This way I haven't had any more shorts which is the good thing at least. But another annoying thing is I have tiny burn marks on the sides of the device.
RE: How the heck do you solder SMD's that have pads underneath?
RE: How the heck do you solder SMD's that have pads underneath?
immediate good options to control paste thickness and placement. The best I can do is use the fine tip syringe.
RE: How the heck do you solder SMD's that have pads underneath?
A similar issue GND under the IC was solved by creating TWO holes !
The BIG hole allow solder and the small hole allow to check with an Ohm Meter
if the solder attach the ground of the IC to the common circuit GND
As good Engineering practice avoid using IC's that have conductors under the IC
Any question please-daveross100@gmail .com