TSSOP Exposed Pad - How do I solder?

Nick. skrev:

put a few large(r) vias in the pad for the exposed flag, then you can solder if from the underside side using a nomal soldering iron through the vias.

maybe a hack, but better than nothing...

-Lasse

Reply to
langwadt
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Chris Jones skrev:

agreed, solder moves toward the hottest place, so heat one via and adding solder at another should work.

and if the flag is there to help get the heat out of the chip its probably a good idea to have as many vias as possible (with no thermal relief) anyway

size is always up for discussion ;)

-Lasse

Reply to
langwadt

As a hobbyist, I've never needed to use SMD before. I now want to make a circuit based on the Linear Lt3474:

Only availiable in TSSOP. However, I notice that the exposed pad ("pin

17") must be connected to ground according to the datasheet. To me that means soldered.

How might I do this?

Reply to
Nick.

In article , "Nick." writes: |> Only availiable in TSSOP. However, I notice that the exposed pad ("pin |> 17") must be connected to ground according to the datasheet. To me that |> means soldered. |> |> How might I do this?

Make a wide (>1.5mm) plated via in the middle of the pad (ie. a double sided PCB) and use a powerful soldering iron at the backside...

--
         Georg Acher, acher@in.tum.de
         http://www.lrr.in.tum.de/~acher
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Reply to
Georg Acher

PCB)

I'm doing the same, is it better to use 2 or more vias, with smaller holes?

martin

Reply to
martin griffith

I like to use several vias large enough to be able to fit very fine solder wire down them. If I feed solder down one hole and it comes up another hole then I figure that at least part of the paddle must be properly attached.

Some other people have different ideas from me on the subject of the via size.

Chris

Reply to
Chris Jones

I have a local guy who puts things like this down for me. I put the recommended pad on the board (both sides, because it's for heat transfer anyway) and he simply puts it in position after dropping some solder on pins and pads and blasts it with a hot air gun.

Works a treat.

Cheers

PeteS

Reply to
PeteS

Thinking along the same limes here, wonder if there is a spice model (joke)

martin

Reply to
martin griffith

This may sound a bit off the wall, but you may find it easier to pre-heat the board prior to / while soldering. While there is professional equipment to do this, it is way too expensive for the hobbyist. However, a electric hotplate works too, you just have to be carefull not to burn yourself while working. I have seen articles (searched for solder and hot plate) showing how to use this technique.

Another solution that works well, is the use of a toaster oven in place of a reflow oven, but this requires the use of solder paste. If you are interested in this method, again suggested temperature time profiles can be found on line. I actually know someone who sucessfully built a DSP based system board this way, so it isn't all that far fetched.

Reply to
Noway2

PCB)

I've used two 70-mil vias with the LT1976 with good success. The 70-mil vias allowed me to get a tip all the way down into one hole and feed solder through the other. To do this you pretty much need to have a solder mask on the top of the board to isolate the heat tab from the pins. When you have enough solder, you see the level begin to rise in the vias. Surface tension and solder mask keeps the solder from flowing beyond the tab. Two things that I have found make this work better are injecting some liquid solder flux in the vias from the back and using a hot air gun to preheat the board before starting to solder.

Good luck.

--
James T. White
Reply to
James T. White

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