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small company people: how do you handle the Analog Devices LFCSP parts ?

Question for the small company people / consultants: How do you handle the Analog Devices LFCSP parts ?

There's a growing trend for Analog Devices to bring out parts in only the LFCSP package. For example the just announced AD8336 VCA and the ADXL320 accelerometer.

The LFCSP is impossible to tack down with a soldering iron because the pads are underneath the part. Only melting solder paste with some sort of heat gun will work, and a very accurate touch to spread it only on the tiny pads. In comparison the TSOP and SOT-23 size SMT parts are easy.

So, what do you do if you want to try out the part in your circuits? Just buy the eval board and make do? Or are these parts only targeted at the big companies that can afford to have stenciled SMT runs?

Reply to
mw
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I have successfully soldered an LT5506 to a board. You get the thermal pad underneath by putting a big via smack in the middle, and you can get the side contacts with a fine-tip soldering iron and a lot of cursing.

If I start doing a lot of them in those packages I'm going to investigate the toaster-oven reflow machines, for sure.

--

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Reply to
Tim Wescott

No. we built a vapour soldering machine :

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A low cost commercial product with temperature controller to automate the vapour height is on its way.

I don't use paste masks and paste but prefer presoldered pads.

Rene

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Reply to
Rene Tschaggelar

Have you actually tried it yet (it sounds like you have). It looks to me like you could solder it on the sides. You should be able to get the big central pad by using a via and poking solder down it while applying a big soldering iron. Hopefully the "thermal vias" will conduct both ways :)

It looks like I will need to try this myself soon...

--

John Devereux
Reply to
John Devereux

John,

We use one of those fancy hot-air based "rework" stations (that has the video attachment to let you line things up) and either a pneumatic paste dispenser or laser-cut solder paste masks and Xacto knife-sized applicators (we have a handful of paste masks for the common packages we use. This is probably upwards of $10k in equipment, however, so depending on just how "small" you are it may not be an option. In a pinch, I've made boards where I've just stuck a really big via (big enough for a really skinny toldering iron tip) in that center pad and then manually soldered it down. It works quite well (for hand assembly -- for proper reflow assembly I expect it wouldn't work well t all), and electrically you've made a really good, low-impedance connection to ground.

---Joel

Reply to
Joel Kolstad

I've soldered them by tacking down two opposite corners with a fine tip (it is a bit tricky) then applying plenty of gel flux and drag soldering each row of contacts with a larger tip. I also use a large via in the middle of the thermal pad, heating it up with a large tip and feeding in solder.

Leon

Reply to
Leon

Excellent! I was hoping I could do exactly this.

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John Devereux
Reply to
John Devereux

It helps if you make the pads a bit longer on the PCB so that you can get soldering iron on to the pad

-Lasse

Reply to
langwadt

What's wrong with a simple handheld hot-air rework station?

Best regards, Spehro Pefhany

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Reply to
Spehro Pefhany

Hmmm... you think I should invest in one? Any recommendations? There is still the problem of getting the paste onto the 48 x 0.5mm pitch pads.

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John Devereux
Reply to
John Devereux

BTW, the correct mnemonic for small to medium-sized businesses is SMB, according to this week's eWeek. So, the subject should be: Q. How do SMB handle AD's LFCSP?

--
 Thanks,
    - Win
Reply to
Winfield Hill

A long time ago a tech put it this way: "I can't light my cigarette with those" :-)

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Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

You can if you turn it up high enough. ;-)

Cheers! Rich

Reply to
Rich Grise

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