Re: [time-nuts] PCB design questions thread II
John Miles wrote:
For one-off PCBs, I've had good luck with www.batchpcb.com .
I agree. I've used them once and have been happy with the
results, you just can't be in any hurry. Unfortunately,
there's no indication of how long it will take a priori.
SMD is not hard to work with by hand, down to 0603 or thereabouts
depending on eyesight and/or equipment. I find it easier to deal
with than through-hole, frankly.
I agree with the first part, but I actually find SMD to be easier
than T/H, if you stick with 0603 and larger for the passives. I
find SMD not only easier but quite bit a faster.
SMD IC packages are easy once you get the hang of them, but a
microscope is needed for inspecting and fixing fine pitched parts.
(I think this is a bit of surprise to some folks.)
Personally I hate turning boards over and clipping leads.
And I'd much rather layout SMD than T/H.
-ch
At 08:04 PM 6/2/2008, you wrote:
Personally I hate turning boards over and clipping leads.
And I'd much rather layout SMD than T/H.
A man after my own heart. 0.5mm and even 0.4mm pin pitch is fine, QFN
is doable, but takes patience sadly BGA is a bit beyond the pale for
me right now until I get some more gear. Until I started the job I
have now I hadn't done any PTH in nearly 15 years - and now I know
why! And now I know why we have technicians to assemble prototypes,
but none of them can outdo me for speed and accuracy on an 0.5mm PQFP FPGA.
If you are going to do a lot of SMT work by hand, then a good stereo
microscope and a Metcal MX500 series iron are almost indispensable.
John
christopher hoover wrote:
John Miles wrote:
For one-off PCBs, I've had good luck with www.batchpcb.com .
I agree. I've used them once and have been happy with the
results, you just can't be in any hurry. Unfortunately,
there's no indication of how long it will take a priori.
SMD is not hard to work with by hand, down to 0603 or thereabouts
depending on eyesight and/or equipment. I find it easier to deal
with than through-hole, frankly.
I agree with the first part, but I actually find SMD to be easier
than T/H, if you stick with 0603 and larger for the passives. I
find SMD not only easier but quite bit a faster.
SMD IC packages are easy once you get the hang of them, but a
microscope is needed for inspecting and fixing fine pitched parts.
(I think this is a bit of surprise to some folks.)
Personally I hate turning boards over and clipping leads.
And I'd much rather layout SMD than T/H.
-ch
However for low frequency work the low thermal mass of resistors and
opamps in smt packages can be problematic.
Also SMT packages are more sensitive to board deflections and vibration.
Using guard rings with some SMT parts is difficult to impossible.
You no longer have the option of directly connecting a leakage sensitive
lead to a virgin teflon standoff.
Mixers and phase detectors with dc and low frequency isolated grounds
for the IF and RF ports dont appear to be available in SMT packages.
How do you cope with SMT parts (eg high frequency ADCs) with metal
thermal transfer /ground connections under the package itself?
Bruce
Quoth Bruce Griffiths at 2008-06-03 09:50...
How do you cope with SMT parts (eg high frequency ADCs) with metal
thermal transfer /ground connections under the package itself?
Haven't done it myself, but interested to hear others experiences. I'm
guessing that this would be a job for solder paste and a toaster oven -
or high-tech equivalent.
--
Matthew Smith
Smiffytech - Technology Consulting & Web Application Development
Business: http://www.smiffytech.com/
Personal: http://www.smiffysplace.com/
LinkedIn: http://www.linkedin.com/in/smiffy
How do you cope with SMT parts (eg high frequency ADCs) with metal
thermal transfer /ground connections under the package itself?
"How to succeed the first time with ultra-small QFN packages"
http://www.wirelessnetdesignline.com/showArticle.jhtml?articleID=202800018
A really good way to handle the pad on the bottom of the part is to put a
hole through the board right there. You usually need a bunch of vias to tie
the pad to the ground plane on the bottom of the board anyway. Put one hole
large enough for your soldering iron tip to reach in and touch the underside
of the part. When installing the part, solder the regular pads first, then
flip the board over and solder the central pad.
This is sort of self limiting too. If you apply too much heat for too long,
the part desolders itself and falls off!
Adding the extra hole is recommended by some of the vendors. I've used it
sucessfully with 2.4GHz band radios and it works great.
Keith
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Bob Paddock
Sent: Monday, June 02, 2008 6:24 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] PCB design questions thread II
How do you cope with SMT parts (eg high frequency ADCs) with metal
thermal transfer /ground connections under the package itself?
"How to succeed the first time with ultra-small QFN packages"
http://www.wirelessnetdesignline.com/showArticle.jhtml?articleID=202800018
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Quoth Bruce Griffiths at 2008-06-03 09:50...
How do you cope with SMT parts (eg high frequency ADCs) with metal
thermal transfer /ground connections under the package itself?
Haven't done it myself, but interested to hear others experiences. I'm
guessing that this would be a job for solder paste and a toaster oven -
or high-tech equivalent.
Yes, see the link I posted. Solder paste + heat gun does the trick, or you
can just carve out a hole for your soldering iron tip with a Dremel tool.
Even BGAs are commonly soldered at home with toaster ovens.
-- john, KE5FX
Another option is to cook the boards in a skillet.
http://www.sparkfun.com/commerce/present.php?p=Reflow%20Skillet
While John may be brave enough to hand solder BGA I am not :-)
Shorts can be easily detected with x-ray, but opens can be quite difficult
to spot.
If you do endup hand soldering BGA, this is a good tool to check shorts and
opens. That is, if the part is JTAG enabled.
http://www.macraigor.com/jscan.htm
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of John Miles
Sent: Monday, June 02, 2008 7:27 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] PCB design questions thread II
Quoth Bruce Griffiths at 2008-06-03 09:50...
How do you cope with SMT parts (eg high frequency ADCs) with metal
thermal transfer /ground connections under the package itself?
Haven't done it myself, but interested to hear others experiences. I'm
guessing that this would be a job for solder paste and a toaster oven -
or high-tech equivalent.
Yes, see the link I posted. Solder paste + heat gun does the trick, or you
can just carve out a hole for your soldering iron tip with a Dremel tool.
Even BGAs are commonly soldered at home with toaster ovens.
-- john, KE5FX
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Quoth John Miles at 2008-06-03 11:56...
Quoth Bruce Griffiths at 2008-06-03 09:50...
How do you cope with SMT parts (eg high frequency ADCs) with metal
thermal transfer /ground connections under the package itself?
Haven't done it myself, but interested to hear others experiences. I'm
guessing that this would be a job for solder paste and a toaster oven -
or high-tech equivalent.
Yes, see the link I posted. Solder paste + heat gun does the trick, or you
can just carve out a hole for your soldering iron tip with a Dremel tool.
Yes - thanks for that, it was interesting reading. Think I might post
that link over on the Homebrew PCB list, as I know that the question has
been asked there fairly recently.
Cheers
M
--
Matthew Smith
Smiffytech - Technology Consulting & Web Application Development
Business: http://www.smiffytech.com/
Personal: http://www.smiffysplace.com/
LinkedIn: http://www.linkedin.com/in/smiffy
Bruce Griffiths bruce.griffiths@xtra.co.nz wrote:
How do you cope with SMT parts (eg high frequency ADCs) with metal
thermal transfer /ground connections under the package itself?
Put a plated-through hole in the board under the part, with a pad to
match the part's ground/heatsink pattern. Make the plated-through
hole big enough to stick a blunt soldering iron point through. Pretin
the board, push the part on while heating the back of the SMT through the hole,
flow solder in through the hole.
But lots of folks are using solder paste and toaster ovens
anyway today for BGA's etc. and then it's no big deal at all.
Has worked great for me in multiple AD9954 designs (400 MHz 14-bit DAC
for DDS is the key... is 400MHz high frequency anymore? It was several
years ago!).
Tim.