Re: small soldering job


"Walter Harley" <walterh@xxxxxxxxxxxxxxxxxxxx> a écrit dans le message de
news:c9CdnY5u1L--3QrfRVn-2w@xxxxxxxxxxxxxxxx
> "Spehro Pefhany" <speffSNIP@xxxxxxxxxxxxxxxxxxxxxxx> wrote in message
> news:g1kd915iplq6cdsd03uq2upeig2kqkmkc5@xxxxxxxxxx
> > Hot air works okay for them too, at least for a few prototypes. I have
> > not tried a QFN44 or 28 yet, but they don't look too scary.
>
> I'm assuming we're all talking about the same thing, chips with a
heat-sink
> pad in the center that is intended to be soldered directly to a pad on the
> component side of the PCB, that in turn is connected with thermal vias to
> more copper on the other side of the PCB. The problem being that the pad
is
> between PCB and chip, and therefore not accessible.
>
> How do you get solder to the hidden pad? And, are you applying the hot
air
> from the component side or the other side?
>
> I like Paul's idea of leaving a hole big enough to get the solder in from
> the bottom.
>

The pad in itself won't do much for power dissipation. You have to connect
it through a bunch of vias to some plane that'll spread heat across the PCB
more efficiently.

As Paul said, make one or more vias bigger so that you can solder the
package through them.


--
Thanks,
Fred.


.

Relevant Pages

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