Parts Selection
0.5 mm TSSOP, MSOP and QFPs are not fun but OK. 0.65 is considerably easier, not only to assemble, but also if you have to put a scope probe tip on one of the pins. I can work with 0.65 without magnifier, 0.5 I can't.
QFNs are a no-no for me in the current state of affairs, even though I see the day coming soon where I will have to get equipped just because there are interesting parts only available in QFN packages.
0805 parts are also OK, smaller probably not if I have a choice. I understand that with microwave circuits, you sometimes have to use smaller packages to match line width. That sucks.
I just finished building a couple of prototypes with 0805 passives, SOIC and MSOP and 0.65 QFPs (about 120 parts total each board) and while it does not look very good, both worked the first time. I had to do it myself because my assembler was not available and I needed to check these protos. The assembler will build the next 10. It took me about 4 hours to build 2 boards. I used a fine tip, temperature controlled soldering iron and a magnifier mounted on a old pair of recycled sunglasses :)
I am now seriously looking at a hot air rework station and an oven because that's just the only way forward.
If someone can recommend a solder paste dispenser that works better than a seringe, I would be interested.
Didier KO4BB
Sent from my BlackBerry Wireless thingy while I do other things...
-----Original Message-----
From: "Bob Camp" lists@rtty.us
Sender: time-nuts-bounces@febo.com
Date: Fri, 25 Mar 2011 13:07:32
To: 'Discussion of precise time and frequency measurement'time-nuts@febo.com
Reply-To: Discussion of precise time and frequency measurement
time-nuts@febo.com
Subject: [time-nuts] Parts Selection
Hi
Just a show of hands sort of thing. It comes up each time we talk about
projects and never really gets answered. Rather than trying to work it out
as a part of a project, let's see if it can be addressed by it's self.
How many people are willing to solder up a project with multiple 0.5mm
spacing >=144 pin package IC's on it? There's a typical package drawing at
the end of:
http://www.national.com/ds/DP/DP83816EX.pdf
I'm sure it's a "what's in it for me?" sort of question. Let's assume it's
just neat piece of bench gear rather than a home grown cesium standard for
$100.
I don't think this part really matters, but it might to some people. Say
each chip is well below $100, but above $20 each. There might be only one
part like this on some projects, but for the sake of this poll, let's say
there are two or three of them. Net is roughly 250 to 500 pins like this to
solder, on some number of packages. It's part of a project that will cost
you $250 to $500.
I'm not talking about opinions on weather it can or can't be done. It
certainly can be done and is done every day. What I'm asking is - would you
buy a bag with the parts all in it? If you do are you going to put it
together in a reasonable amount of time? Reasonable time might mean
different things to different people. For the sake of completeness, yes you
also need to get it working after you assemble it.
Next layer (you knew there had to be more) - have you done it before
(anywhere)? / done it in the last 2 years (at home)? / are you set up to do
it today (at home)?
I'm not trying to get into "how would you do it / what would you need /
could you farm it out". Those are also neat questions, but not part of this.
I'll start off the voting (and yes the answers are out of order):
Done it in the before - yes.
Done it in the basement / last 2 years - no.
Set up to do it in the basement - yes, but not set up well.
Would I buy one - done that before. Likely would again. (counts as a yes).
Would actually do it in a reasonable amount of time - unlikely. (That
counts as a no).
Any more votes?
Bob
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Hi
There are machines out there that are essentially robotic syringes. Several outfits make them. They can also be used to put down adhesive. I don't know of anybody who actually likes them.
Best bet - get / make a simple screen printer. A manual one is going to be cheap. A home made one is even cheaper. The solder screen it's self won't cost you much more than the time you would spend programming the robot and messing with it. Solder screen / stencil generation is a "push button" sort of thing with a modern pcb layout program.
Bob
On Mar 26, 2011, at 8:40 AM, shalimr9@gmail.com wrote:
0.5 mm TSSOP, MSOP and QFPs are not fun but OK. 0.65 is considerably easier, not only to assemble, but also if you have to put a scope probe tip on one of the pins. I can work with 0.65 without magnifier, 0.5 I can't.
QFNs are a no-no for me in the current state of affairs, even though I see the day coming soon where I will have to get equipped just because there are interesting parts only available in QFN packages.
0805 parts are also OK, smaller probably not if I have a choice. I understand that with microwave circuits, you sometimes have to use smaller packages to match line width. That sucks.
I just finished building a couple of prototypes with 0805 passives, SOIC and MSOP and 0.65 QFPs (about 120 parts total each board) and while it does not look very good, both worked the first time. I had to do it myself because my assembler was not available and I needed to check these protos. The assembler will build the next 10. It took me about 4 hours to build 2 boards. I used a fine tip, temperature controlled soldering iron and a magnifier mounted on a old pair of recycled sunglasses :)
I am now seriously looking at a hot air rework station and an oven because that's just the only way forward.
If someone can recommend a solder paste dispenser that works better than a seringe, I would be interested.
Didier KO4BB
Sent from my BlackBerry Wireless thingy while I do other things...
-----Original Message-----
From: "Bob Camp" lists@rtty.us
Sender: time-nuts-bounces@febo.com
Date: Fri, 25 Mar 2011 13:07:32
To: 'Discussion of precise time and frequency measurement'time-nuts@febo.com
Reply-To: Discussion of precise time and frequency measurement
time-nuts@febo.com
Subject: [time-nuts] Parts Selection
Hi
Just a show of hands sort of thing. It comes up each time we talk about
projects and never really gets answered. Rather than trying to work it out
as a part of a project, let's see if it can be addressed by it's self.
How many people are willing to solder up a project with multiple 0.5mm
spacing >=144 pin package IC's on it? There's a typical package drawing at
the end of:
http://www.national.com/ds/DP/DP83816EX.pdf
I'm sure it's a "what's in it for me?" sort of question. Let's assume it's
just neat piece of bench gear rather than a home grown cesium standard for
$100.
I don't think this part really matters, but it might to some people. Say
each chip is well below $100, but above $20 each. There might be only one
part like this on some projects, but for the sake of this poll, let's say
there are two or three of them. Net is roughly 250 to 500 pins like this to
solder, on some number of packages. It's part of a project that will cost
you $250 to $500.
I'm not talking about opinions on weather it can or can't be done. It
certainly can be done and is done every day. What I'm asking is - would you
buy a bag with the parts all in it? If you do are you going to put it
together in a reasonable amount of time? Reasonable time might mean
different things to different people. For the sake of completeness, yes you
also need to get it working after you assemble it.
Next layer (you knew there had to be more) - have you done it before
(anywhere)? / done it in the last 2 years (at home)? / are you set up to do
it today (at home)?
I'm not trying to get into "how would you do it / what would you need /
could you farm it out". Those are also neat questions, but not part of this.
I'll start off the voting (and yes the answers are out of order):
Done it in the before - yes.
Done it in the basement / last 2 years - no.
Set up to do it in the basement - yes, but not set up well.
Would I buy one - done that before. Likely would again. (counts as a yes).
Would actually do it in a reasonable amount of time - unlikely. (That
counts as a no).
Any more votes?
Bob
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To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
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and follow the instructions there.
On 26/03/2011, Bob Camp lists@rtty.us wrote:
Best bet - get / make a simple screen printer. A manual one is going to be
cheap. A home made one is even cheaper. The solder screen it's self won't
cost you much more than the time you would spend programming the robot and
messing with it. Solder screen / stencil generation is a "push button" sort
of thing with a modern pcb layout program.
plastic stencils are cheap, I get mine from
http://www.smtstencil.co.uk/
No need for any machinery, just tape it to the board, then squeegee
the paste using a credit card. Works fine, for low volume, and is
easily capable of 0.5mm pitch.
More of a concern, if issuing kits of parts, is how to deliver
fine-pitch QFPs with their legs intact. The best way to package them
for shipping may well be to attach them to a PCB with some kind of
melted metal...
(This is probably my first post here. Hobbyist / engineer running an
old but adequate True-time GPS and Rubidium , to keep the test gear
(sufficiently) truthful.)
Steve
On Fri, Mar 25, 2011 at 5:29 PM, Bob Camp lists@rtty.us wrote:
I don't see a way to reasonably ship a solder mask with each board. I agree
it would be neat, but it would cost ...
Solder Stencil actually. The mask is part of the board.
Low use stencils are $25: http://www.pololu.com/catalog/product/446
for each one.
I'll address some other comments I see in this thread, in this one reply.
On the PCB list the consensus is 0402's are the smallest things that
can be done by hand.
0603 are no problem at all to do by hand.
BGA's are actually easier to do than QFN parts, as long as you accept
the board is now not repairable and is a throwaway item.
Avoid QFN's if at all possible, especially in battery powered
circuits. The flux gets trapped raising leakage currents.
It doesn't take "a steady hand" it takes a while timed hand, drop as
pass over not hold and aim. Think Target Shooting rather than holding
absolutely still.
I expect any Time Nut probably has what it takes to cobble together a
video magnifier in their house already, except for maybe the macro
lenses, for example:
http://www.designer-iii.com/Solder/ made from Wife's video camera, RF
Modulator and old color TV. Check out the Toy Store for Cyclops
Camera or search for AE10324-ND at http://www.digikey.com .
Not the best but works. Works well mounted on old desk lamp base,
that has a flexible neck to aim and hold, picked up at the Salvation
Army Thrift Store.
Also consider there maybe disruptions in the supply chain due to the
Japan Earthquake at the fundamental material level, as well has the
chip level. Many fabs are still closed due to damage or lack of
reliable power.
"The glue that holds the electronic industry together falls apart,
Bismaleimide Triazine (BT) resin shortage."
http://blog.softwaresafety.net/2011/03/glue-that-holds-electronic-industry.html
--
http://blog.softwaresafety.net/
http://www.designer-iii.com/
http://www.wearablesmartsensors.com/
Bob Paddock wrote:
...
BGA's are actually easier to do than QFN parts, as long as you accept
the board is now not repairable and is a throwaway item.
...
BGA's are about as easy to rework as anything else. You use a hot air
rework station, and an underboard preheater. The hot air rework station
has a manifold that constrains the hot air to heat the entire top surface
of the BGA, and when the solder melts, the chip will pop right off.
The big problem is you cannot readily re-ball a BGA part if it turns out to
be good, and you want to reuse it. Re-balling machines are rather expensive
things. You must do a good job of wiping away the old solder from the pcb
while it is still hot, and clean up the left over solder debris, and flux.
If you look on youtube, there are quite a few videos showing guys replacing
video "cards" on laptop computers. They are all BGA, and the videos give a
good idea of what is involved.
-Chuck Harris
Didn't know that outfit, thanks for the link. :) Would you say they are durable
enough to say 5 boards with it? (I would hope so, but you never know...)
With regard to the delivery of the fine pitch stuff ... as long as the one
putting together the kit is ordering those as cut-tape then that should be no
problem.
Just cut the tape into smaller strips and include those with the kit.
regards,
Fred
----- Original Message ----
From: Steve Wiseman sjwiseman@gmail.com
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Sat, March 26, 2011 3:10:13 PM
Subject: Re: [time-nuts] Parts Selection - Short Run Assembly
On 26/03/2011, Bob Camp lists@rtty.us wrote:
Best bet - get / make a simple screen printer. A manual one is going to be
cheap. A home made one is even cheaper. The solder screen it's self won't
cost you much more than the time you would spend programming the robot and
messing with it. Solder screen / stencil generation is a "push button" sort
of thing with a modern pcb layout program.
plastic stencils are cheap, I get mine from
http://www.smtstencil.co.uk/
No need for any machinery, just tape it to the board, then squeegee
the paste using a credit card. Works fine, for low volume, and is
easily capable of 0.5mm pitch.
More of a concern, if issuing kits of parts, is how to deliver
fine-pitch QFPs with their legs intact. The best way to package them
for shipping may well be to attach them to a PCB with some kind of
melted metal...
(This is probably my first post here. Hobbyist / engineer running an
old but adequate True-time GPS and Rubidium , to keep the test gear
(sufficiently) truthful.)
Steve
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and follow the instructions there.
On Fri, 25 Mar 2011 13:07:32 -0400
"Bob Camp" lists@rtty.us wrote:
Done it in the before
Yes. I regularly solder 0.5mm and 0.63mm pitch stuff by hand at work.
Done it in the basement / last 2 years - no.
No. I take all the stuff i want to solder to work and do it there.
Although i have equipment at home that would allow me to get everything
soldered with a reasonable confidence, the equipment at work allows me
to get it working for sure. And being able to check the solder points
under a microscope is a nice thing, before you fry something because
of a short that you havent seen. :-)
We have a reflow oven at work as well, but we hardly ever use it,
as we get better results by hand than with the oven.
Set up to do it in the basement
Yes, but not well, see above.
Ok, i have to relativate here, i'm not well equipped in reference
to a professional lab. For a hobbist, i have quite good stuff.
Would I buy one
Yes
Would actually do it in a reasonable amount of time
500 pins? That's probably a day or two for me. Depending on the layout
and the exact mix of components.
Attila Kinali
--
The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
-- Tirin, The Dispossessed, U. Le Guin