[time-nuts] Parts Selection

Fri Mar 25 17:49:22 UTC 2011

Hi

What ever technique has worked for you in the past is "legal" as far as this
poll is concerned. I suspect we could go on for quite a while about what is
the best or worst approach. 

For the sake of this poll, let's leave the 0402's out. There certainly are
issues there, but I'd rather not get them into this. There likely would be
surface mount passives on the board, but for now let's say they are "big"
without trying to define that. We could ultimately run another poll.

Obviously the idea of all this is to come up with some sort of design
guidelines for projects. That's going to take a bit more work than looking
at just one part. 

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Heinzmann, Stefan (ALC NetworX GmbH)
Sent: Friday, March 25, 2011 1:37 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Parts Selection

Hi,

I have done this sort of stuff multiple times, and am prepared to do it
again (in the basement) as long as my eyes are good enough and my hands
steady.

0.5 mm pin pitch is certainly doable with a soldering iron. The trick is to
not be afraid of shorting pins. I often pull a reasonable amount of solder
across all pins, which shorts them all together, and remove the excess
solder with a wick afterwards. It needs a bit of practicing, so best obtain
a few cheap components that can be destroyed. Particularly fine tips are not
necessary on the soldering iron. They could even be counterproductive.

The thing I can't handle at present is ball grid arrays and other parts that
need solder underneath. More and more parts are coming in those packages
exclusively, and I may have to experiment with ovens...

I work with passives down to 0603. I have had to work with 0402, and found
them a pain. I couldn't handle 0402 in any reasonable way except when using
a hot air (or hot gas) soldering iron.

Cheers
Stefan

-----Ursprüngliche Nachricht-----
Von: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] Im
Auftrag von Bob Camp
Gesendet: Freitag, 25. März 2011 18:08
An: 'Discussion of precise time and frequency measurement'
Betreff: [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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