[time-nuts] time-nuts Digest, Vol 47, Issue 5

Don Collie jnr merdon at xtra.co.nz
Mon Jun 2 22:21:27 EDT 2008


I`m curious : What is a "virgin teflon standoff", and does it have anything 
to do with the "teflon Don"?
I don`t see much SMD, here, at the extreme edge of the known Universe, but I 
can see that the single sided approach would make tracing a circuit  much 
easier,......
...........................................................................Don 
C.

PS : Perhaps the "double sided approach" would be more suitable for 
Schitzophernics - a few of whome it has been my pleasure to meet.

----- Original Message ----- 
From: <time-nuts-request at febo.com>
To: <time-nuts at febo.com>
Sent: Tuesday, June 03, 2008 1:53 PM
Subject: time-nuts Digest, Vol 47, Issue 5


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> Today's Topics:
>
>   1. Re: PCB design questions thread II (John Day)
>   2. Re: PCB design questions thread II (Bruce Griffiths)
>   3. Re: PCB design questions thread II (Matthew Smith)
>   4. Re: PCB design questions thread II (Bob Paddock)
>   5. Re: PCB design questions thread II (Matthew Smith)
>   6. Re: PCB design questions thread II (Bob Paddock)
>   7. Re: PCB design questions thread II (Chuck Harris)
>   8. Re: PCB design questions thread II (Bob Paddock)
>   9. Re: PCB design questions thread II (Keith Payea)
>  10. Re: PCB design questions (Didier Juges)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Mon, 02 Jun 2008 20:20:14 -0400
> From: John Day <johnday at wordsnimages.com>
> Subject: Re: [time-nuts] PCB design questions thread II
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <mailman.2641.1212458003.2318.time-nuts at febo.com>
> Content-Type: text/plain; charset="us-ascii"; format=flowed
>
> 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
>
>
>
>
> ------------------------------
>
> Message: 2
> Date: Tue, 03 Jun 2008 12:20:26 +1200
> From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
> Subject: Re: [time-nuts] PCB design questions thread II
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <48448E4A.1080309 at xtra.co.nz>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> 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
>
>
>
> ------------------------------
>
> Message: 3
> Date: Tue, 03 Jun 2008 10:04:44 +0930
> From: Matthew Smith <matt at smiffytech.com>
> Subject: Re: [time-nuts] PCB design questions thread II
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <484491A4.4020809 at smiffytech.com>
> Content-Type: text/plain; charset=UTF-8; format=flowed
>
> 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
>
>
>
> ------------------------------
>
> Message: 4
> Date: Mon, 2 Jun 2008 20:34:43 -0400
> From: Bob Paddock <bob.paddock at gmail.com>
> Subject: Re: [time-nuts] PCB design questions thread II
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <200806022034.44056.bob.paddock at gmail.com>
> Content-Type: text/plain;  charset="iso-8859-1"
>
> On Monday 02 June 2008 02:31:18 pm Patrick wrote:
>
>> I have wanted to fabricate my own PCBs for several years now but I have
>> never made an attempt. I am set up here to do silk screening and I have
>> ovens and a hot-air soldering iron. Has anyone else tried to fabricate
>> their own boards or is the price of farming the work out just so low now?
>
> I've played with doing them at work.  Found it better to just farm them 
> out
> to the prototype house.  It is tough to get any real consistency from week 
> to
> week.
>
>> If anyone has farmed out work, could you please feedback as to the entry
>> level costs and if possible, some suggested companies?
>
> Cheapest place I've come across for easy boards with 10mil or large lines
> is this one, but I've not used them yet (probably next month I will):
>
> http://www.futurlec.com/PCBService.shtml
>
>> > 1. Surface mount or through hole?  I don't have a re-flow oven (or even 
>> > a
>> > hot air soldering system), so my inclination is to use through hole
>
> SMT is actually easier if you have a good magnifying system.  I use
> macro-lenses on the wife's Cam-Corder:
>
> http://www.designer-iii.com/Solder/  Looks better than the picture of the
> screen shows in reality.
>
> http://www.micromark.com/ has the type of tools that you need, like 
> insulated
> and cross-tweezers (squeeze them to open them, the reverse of normal
> tweezers) etc.
>
> Pick up a small convection oven at Wal-Mart or such place.
>
> If your making several get a Stencil:
>
> http://www.smtstencil.com/
> http://www.customlasercutting.com/
>
>>   Will using through hole cause me grief?
>
> In the long term, yes.  A lot of older TH parts have not been updated to 
> ROHS
> (Lead Free) and they never will be, they will be discontinued at some 
> point.
> Virtually all new parts are SMT.
>
>> > 2. How many layers?   In an ideal world with money no object, if I
>> > understand the current art correctly, I think I'd probably aim for a 
>> > five
>> > layer
>
> I assume that is a typo?  You can not have an odd number of layers.
> In this current 3D reality each layer has two sides.  :-)
>
>> > board with Vcc, Digital Ground and Power Ground being separate
>> > internal planes, and trace routing on the top and bottom of the board
>> > with as few vias between top and bottom as possible.  Does that sound
>> > right?
>
> Separate ground planes, or split ground planes are a bad idea in this 
> context.
> Always think about where the return current is going to flow.
> Read the Analog Devices seminar notes on the subject.
>
> http://www.analog.com/analog_root/static/library/technicalSeminarSeries.html
> is the link to the books but you can find the chapters on line.
>
> Read 7a & 7b if nothing else:
>
> http://www.analog.com/en/DCcList/0,3090,1073%255F%255F961,00.html
>
>
> -- 
>                http://www.wearablesmartsensors.com/
> http://www.softwaresafety.net/ http://www.designer-iii.com/
>                 http://www.unusualresearch.com/
>
>
>
> ------------------------------
>
> Message: 5
> Date: Tue, 03 Jun 2008 10:08:03 +0930
> From: Matthew Smith <matt at smiffytech.com>
> Subject: Re: [time-nuts] PCB design questions thread II
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <4844926B.6060105 at smiffytech.com>
> Content-Type: text/plain; charset=UTF-8; format=flowed
>
> Quoth Bob Paddock at 2008-06-03 10:04...
>
>> Cheapest place I've come across for easy boards with 10mil or large lines
>> is this one, but I've not used them yet (probably next month I will):
>>
>> http://www.futurlec.com/PCBService.shtml
>
> I was looking at these - they actually do overseas shipments for
> near-domestic freight prices.  Great for those of us living in countries
> where board houses require arm, leg and first-born for even small/simple
> jobs.
>
> -- 
> 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
>
>
>
> ------------------------------
>
> Message: 6
> Date: Mon, 2 Jun 2008 20:39:02 -0400
> From: Bob Paddock <bob.paddock at gmail.com>
> Subject: Re: [time-nuts] PCB design questions thread II
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <200806022039.02202.bob.paddock at gmail.com>
> Content-Type: text/plain;  charset="iso-8859-1"
>
> On Monday 02 June 2008 04:53:17 pm SAIDJACK at aol.com wrote:
>
>> Not the cheapest, but great for "professional" proto's when quality 
>> trumps
>> cost (above 1GHz, one source FR4 is totally different from another 
>> sources
>> FR4...)
>
> Anyone have suggestions for Metal Core Protype Boards?
> Used in high power LED applications.
>
> I know of this one, are there others?:
> http://www.protoexpress.com/content/speciality.jsp
>
> http://www.cif.fr/new/produits_aff.php3?cat=1&scat=3&sscat=89&p=211
>
>
>
> ------------------------------
>
> Message: 7
> Date: Mon, 02 Jun 2008 21:05:09 -0400
> From: Chuck Harris <cfharris at erols.com>
> Subject: Re: [time-nuts] PCB design questions thread II
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <484498C5.5030806 at erols.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Bob Paddock wrote:
>
>>>> 2. How many layers?   In an ideal world with money no object, if I
>>>> understand the current art correctly, I think I'd probably aim for a 
>>>> five
>>>> layer
>>
>> I assume that is a typo?  You can not have an odd number of layers.
>> In this current 3D reality each layer has two sides.  :-)
>
>
> Sure you can.  I have done 3 layer, 5 layer, and 7 layer boards.
>
> Having done those, I will advise you not to do 3 layer, it warps.  But
> everything else is easily do able.
>
> Multilayer boards are done by bonding together combinations of
> 1 side, 2 side, and 0 sided laminate.  For instance:
>
> 4 layer can be made by:
>
> 2 side | 0 side | 2 side
> 1 side | 2 side | 1 side
> 1 side | 1 side | 2 side
>
> ...
>
> 5 layer can be made by:
>
> 2 side | 1 side | 1 side | 1 side
> 2 side | 0 side | 2 side | 1 side
> 2 side | 1 side | 0 side | 2 side
>
> ...
>
> 6 layer can be made by:
>
> 2 side | 0 side | 2 side | 0 side | 2 side
> ...
>
> The only down side to odd numbers of layers is the supply house
> has to stock 1 sided laminate.
>
> -Chuck Harris
>
>
>
> ------------------------------
>
> Message: 8
> Date: Mon, 2 Jun 2008 21:24:21 -0400
> From: Bob Paddock <bob.paddock at gmail.com>
> Subject: Re: [time-nuts] PCB design questions thread II
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <200806022124.21583.bob.paddock at gmail.com>
> Content-Type: text/plain;  charset="iso-8859-1"
>
>
>
>> 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
>
>
>
>
> ------------------------------
>
> Message: 9
> Date: Mon, 2 Jun 2008 18:36:46 -0700
> From: "Keith Payea" <kpayea at bryantlabs.net>
> Subject: Re: [time-nuts] PCB design questions thread II
> To: "'Discussion of precise time and frequency measurement'"
> <time-nuts at febo.com>
> Message-ID: <01e001c8c51a$49d9c810$0a01a8c0 at bryant1>
> Content-Type: text/plain; charset="us-ascii"
>
> 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 at febo.com [mailto:time-nuts-bounces at 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
>
>
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>
>
> ------------------------------
>
> Message: 10
> Date: Mon, 2 Jun 2008 20:52:56 -0500
> From: "Didier Juges" <didier at cox.net>
> Subject: Re: [time-nuts] PCB design questions
> To: "'Discussion of precise time and frequency measurement'"
> <time-nuts at febo.com>
> Message-ID: <012701c8c51c$8c01e630$0a01a8c0 at didierhp>
> Content-Type: text/plain; charset="windows-1250"
>
>
>
>> -----Original Message-----
>> From: time-nuts-bounces at febo.com
>> [mailto:time-nuts-bounces at febo.com] On Behalf Of David C. Partridge
>> Sent: Monday, June 02, 2008 1:20 PM
>> To: 'Discussion of precise time and frequency measurement'
>> Subject: [time-nuts] PCB design questions
>>
>> I've been working on the design for a frequency divider to
>> complement the Thunderbolt I recently bought from TVB (thank
>> you Tom, it's working very well as far as I can tell, though
>> of course I've no other standard to compare against).
>>
>
> Dave,
>
> I just made one using a single microcontroller chip soldered on a 
> Toolstick
> from Silabs. The Toolstick is a small PWB with a small 8051 class
> microcontroller in surface mount package. The Toolstick costs $10 and you
> need a $18 programmer to flash it. I run the uC using the 10 MHz as 
> external
> clock and it has (for now) a 1Hz output.
>
> The toolstick I used is similar to the one described on this page:
>
> http://www.ko4bb.com/Test_Equipment/AFSignalGenerator/SigGen.php
>
> The software is just a couple of for() loops to kill time, a few 2 and 3
> cycles instructions to adjust the timing perfectly (cannot do NOP from C
> with the free compiler, but you can program in assembly if you need to 
> feel
> some pain) and one output is twiddled at the right time. The processor is
> using the 10 MHz as clock. A single chip is all that is required, the chip 
> I
> actually used is a C8051F530-IT, which costs about $4 on the Silabs web 
> site
> (qty 1) and comes in a 20 pin TSSOP package (surface mount, but solderable
> by hand). You really only need to connect 4 pins for that job, supply
> voltage and ground, 10 MHz input and 1Hz output. Silabs has a couple of
> parts that are available in DIP package, notably the C8051F330D (refered 
> to
> as the 330-GP) which is roughly the same core as the 530. If you buy the
> bare chip, you will have to buy the programmer separately, so if you just
> want to build a few simple projects, you are better off buying the
> toolsticks.
>
> You might want to add a D flip-flop to clean up the edge, even though I do
> not know the jitter of the chip itself (I have planned to test it as well 
> as
> I can, but there are more projects in the pipe at the moment than time to
> address them)
>
> I am working on a version with both 1 kHz and 1 Hz outputs.
>
> There are a few sine-to-square converters (clock shapers) on Bruce's page 
> at
>
>
> http://www.ko4bb.com/~bruce/
>
> Didier KO4BB
>
> Internal Virus Database is out-of-date.
> Checked by AVG.
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> 5:24 PM
>
>
>
>
>
> ------------------------------
>
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> End of time-nuts Digest, Vol 47, Issue 5
> **************************************** 




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