You don't need to cut a slot out. It may give more strength I guess but I haven't had a good reason to do that.
When making my own boards I always drill a hole which is big enough that it fits the flat pin, and solder it as is.
I've done this with Serial, parallel, USB, power and other connectors. I haven't had one break the pad off or crack the solder yet.
A lot of commercial boards I've seen also use a round hole rather than a slot.
--- In Homebrew_PCBs@yahoogroups.com, "H. Carl Ott" <hcarlott@...> wrote:
>
> On Tue, Mar 29, 2011 at 8:28 AM, Chris Kleeschulte <laconia@...>wrote:
> >
> >
> > Here is my real question about through hole parts and boards. There are a
> > lot of parts the have flat through hole leads. Of course your drill bit
> > yields a round hole. Even further, some pads intended for those flat (or
> > square pins) are really thin (like 12 mils), such as the .1" pin headers
> > used a lot on dev and breakout boards. The problem I am having is getting a
> > good solid connection to the board with these parts. The pins always seem
> > very precariously attached to the pcb since the pins are attached by so
> > little copper on the board and the different shape between the hole and the
> > pin. Do you guys glue the plastic headers down? Is this a good idea? What
> > about the different shapes? Is the solder supposed to bridge the gap there
> > or is there another way? I know solder really is not a structural
> > component,
> > but without some bonding agent, it really is, right?
> >
> > With SS boards you don't get the strength of the PTH that is normally there
> on DS.
> I try for the smallest possible hole and the maximum amount of copper for
> the pad. Bonding of the copper to the board comes from the adhesives of the
> copper foil to the laminate. Try to maximize that surface area. Bonding
> strength between the part lead and the copper comes from the solder fillet,
> again you want to try to maximize that. Also note that a too hot a soldering
> iron tends to lift pads.
>
> I try to avoid true slotted parts when possible on my toner transfer
> boards, but when necessary I drill multiple holes and bridge them with small
> router bit to open up the slot.
>
> One example of avoiding slotted holes:
> The dirt common 2.1mm power connector comes in the common lug style and an
> uncommon pin style
>
> http://goo.gl/eUypV
> vs
> http://goo.gl/CHu7S
>
> I stock up on the tapered pin style.
>
> -carl
>
>
> [Non-text portions of this message have been removed]
>