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Hand solder LGA16?

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RogerThat:
Hi,

So, I have a board which uses a LIS344 accelerometer. This is a LGA16 package and I'm having some trouble to reliably solder this.

I have tried two different foot print. One, where the solder pads extend outside the package to be able to solder using the normal soldering iron. Then, a second where I made the footprint exactly as the pads (I made a small mistake, ST recommends a footprint which is +0.1mm x and y to the pads).

The last footprint seams to solder nicely, the component re-align it self when the solder starts flowing(using hot-air on the opposite side of the board). But, the connections are not good, I usually end up with just one output working while the others seams to be froozen.

Anyone have any suggestions?

SiliconWizard:
Pre-tin the IC pads, it helps a lot (not too much solder though!)

Shock:
What exact preparation are you doing for reflow? Are you using paste or pretinning, using flux at all? Are you using too much solder or not enough? To add what SiliconWizard said tin both clean and then use flux.

RogerThat:
I've pre-tinned and added flux ( a combination of flux and tin which I know works very well together). I've tried different amount of tin also, from flat to small 'hill'. Both on the component and pad. I usually don't clean between the tinning and adding new flux, can this make a difference?

DaJMasta:
Have you tried with paste?  Pretinned and then just a small dab of solder paste will give you a bit of extra material, but it will be physically sticking up and malleable, so it could aid with reflow.

That said, I'd think pretinned on the IC itself and ample flux would do a pretty good job - is there a substantial connection to the ground plane, perhaps?  If the board underneath isn't reaching soldering temperature because it's wicking away too much heat or has too much thermal mass, when the solder on the IC pads melts, it may just not want to stick to the cooler pads.  If this is the case, preheating the board could help.

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