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How would you mount this package?

Hello,

A magnetometer part I'd like to use - the Honeywell HMC1051Z - is only available in a 8-pin 50 mil pitch SIP package that I've never seen before. The datasheet is available at

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. The pins are too large for me to fit into plated holes if I use "reasonable" design rules (20 mil hole with a 15 mil past the hole annular ring). I asked a technician who suggested surface-mounting by bending the pins into an "L" and then soldering the parts onto 50 mil pitch pads. However, I would rather find a better solution - it seems to me that the first time I brush the part on the board accidentally, I'll rip up the pads!

Does anyone know of a way to mount this part that fits "reasonable" design rules and has some aspect of structural support?

Thank you!

- Nathan

Reply to
Nathan Bialke
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Nathan, That package certainly is a bit of an enigma.

The only other suggestion I could make is soldering the leads flat to traces/pads with the body hanging off the edge of the board or within a cutout segment of the PCB.

The leads seem to be a little short to offset them into two through hole rows, at least not without great care or a good jig to support the leads and not stress the package. It could work but care should be taken and I wouldn't want to do it for any number of devices without a proper jig.

If you did "L" lead them ont SMT pads, bend each leg alternately (left/right, forward/back), that would help with overall support and integrity. Then you would also want to use silicon or epoxy to stabilize the divice for long term reliability.

-- Sincerely, Brad Velander.

Reply to
Brad Velander

Reasonable for what? I consider 20/10 reasonable for the fabs I deal with (pcb-pool can do 12/6, 4pcb can do 15/6). In your case, 20 mil hole with 10 mil annulus gives 10 mil clearance between copper. If I were to etch the board at home (or at the fabs above), I'd do 20 mil hole, 12 mil annulus, and 6 mil space between copper.

Note that to meet the max dimensions, you'd need a 22 mil hole after plating. That leaves 11 mil annulus and 6 mil gap, or 10 mil annulus and 8 mil gap.

If you want more mechanical support, extend the copper pads on the far side of the board perpendicular to the part's axis. They don't have to be round:

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Another option is to stagger the holes, and bend the pins into a stagger pattern, with 25 mil hole and 15 mil annulus:

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Reply to
DJ Delorie

That last one looks pretty much what Honeywell themselves do on the HMR3300 module, which uses the HMC1021Z sensor in the same package. I have a couple of these, and there really isn't much clearance between the round pads.

-- Dave Tweed

Reply to
David Tweed

Why just the far side? Why not the near side too?

--
These are my opinions, not necessarily my employer\'s.  I hate spam.
Reply to
Hal Murray

Well, I've never had problems with parts being pushed through the board. Plus, in PCB, such extensions are done independently, so to add it to both sides would require doing the extension twice. It's not a big deal, I just wouldn't bother.

Also, the larger pads increase the risk of shorts. I'd rather keep the risk down on the component side, as it's not as easy to reach/inspect under the components as it is to do so on the other side.

Actually, I usually don't solder the component side of through-hole pins. I just solder the other side, and let the solder wick through the hole. I don't think the larger pad on the component side would add much mechanical strength in that case; all it would do (if you needed it) is reduce the risk of electrical disconnects due to off-center drills.

Reply to
DJ Delorie

DJ, While your comments sound realistic you are forgetting to deal with the diagonal sizing of the square leads. At maximum tolerances the equivalent round lead is 21.3mils in diameter (sq root of [19mils sq + 9.8mils sq]). Then you must allow tolerance on your hole both for fit and for plating tolerance, I would not specify these holes at less than 28mils finished hole size and preferrably 32mils. Then a minimum annular ring for a soldered through hole pad should be at least 10mils, at that it is more difficult to hand solder with such a small annular ring for soldering contact. So now your pads are at 38 - 42 mils in diameter, your space pad - pad is now 8 -

12 mils. Now throw in soldermask expansion of at least 2 mils and preferrably 4 mils annular ring. You have only got 8 - 0 mils left between pads for soldermask web. All in all it is not a simple footprint when considering all design factors.

Your other comments on hole sizing and annular rings seem to confuse minimum annular rings for vias, verses minimum annular rings for component pads. Suggesting that anyone should/could use a 6 mils annular ring on a component lead is not designing with good practice/reliability in mind.

--
Sincerely,
Brad Velander.

"DJ Delorie"  wrote in message 
news:xnwt0v5og0.fsf@delorie.com...
>
> FYI: please learn to cross post properly.  Don\'t post copies of the
> same message in multiple groups, post one message addressed to
> multiple groups, like this one.
>
>
> Reasonable for what?  I consider 20/10 reasonable for the fabs I deal
> with (pcb-pool can do 12/6, 4pcb can do 15/6).  In your case, 20 mil
> hole with 10 mil annulus gives 10 mil clearance between copper.  If I
> were to etch the board at home (or at the fabs above), I\'d do 20 mil
> hole, 12 mil annulus, and 6 mil space between copper.
>
> Note that to meet the max dimensions, you\'d need a 22 mil hole after
> plating.  That leaves 11 mil annulus and 6 mil gap, or 10 mil annulus
> and 8 mil gap.
>
Reply to
Brad Velander

at

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There are SIL connectors that have a similar pitch, I've made a PCB at home that uses one of them and didn't have any any problems.

Leon

Reply to
Leon

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