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Learning From Others' Mistakes: a Case Study of a PCB Design Error

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Aeroengineer
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Re: OSH Park
Aeroengineer   2/26/2014 9:04:32 PM
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I agree with what you have said here about their value proposition.  I just wish that I could find a similar service that would allow prototyping with .4mm BGA in a similar a la carte fashion.  I cannot justify a prototype for this chip that I want to use with a board size of .38" by .38" and have to pay at least a $100 or more to do it. 

jsloan256
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Re: OSH Park
jsloan256   2/26/2014 9:10:36 PM
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I did a 0.5mm pitch BGA deisgn at OSH Park, but I had to cheat on the escape routing since their width/clearance rules just aren't small enough.  I you find a similar service with finer tolerances than OSH Park be sure to post about it!

Aeroengineer
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Re: OSH Park
Aeroengineer   2/26/2014 9:14:12 PM
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Thanks for sharing.  I will have to take a look, do you detail in your post how you "cheated"?  If not, I would love to hear about it.  I am itching to try a board with the Freescale KL02 chip.  I have thought of a few ways that I might try as you said, cheating the allowables, though not sure if they would work.  For a one off, it might work.

jsloan256
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Re: OSH Park
jsloan256   2/26/2014 9:25:32 PM
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The BGA that I routed was a Xilinx CPLD and only had two concentric rows of pads.  I escaped the inner pads by routing thru (connected to) a pad on the nearby outer row.  This cheat worked because I was only building the design to test my ability to solder BGAs.  I used two separate loads of CPLD code where one or the other connected pads was tristated.

I've seen similar tricks work on large pin count BGAs where only a few of the balls connected to the die.  Inner pads were routed thru external pads that were not connected to the part's die.  Unfortunately it's a such a rare use case that it's almost useless.

Aeroengineer
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Re: OSH Park
Aeroengineer   2/26/2014 9:29:03 PM
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Ah yes.  I had though about perhaps not connecting a few of the outer connections to allow for some of the inner connections.  This still could work if I did not need all the connections, I was just not that hard up on using the chip, but is something that I may yet consider if I really get to the point that I want to use it.  Thanks for sharing!

Etmax
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Re: PCB Shorts
Etmax   2/26/2014 9:55:07 PM
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Well that is of course fair enough, I just wonder whether the the savings are worth it when one considers that our time on earth is rather finite so that time becomes one of our most valuable commodities

Aeroengineer
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Re: PCB Shorts
Aeroengineer   2/26/2014 10:00:08 PM
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Ah yes the opportunity cost of things in life.  In this case, I lost perhaps 2-3 hours.  To pay for a service that offered similar design limits for a proto board, I would have had to work a few extra hours, so it was probably a wash.  Now, if I had my family with me while I was doing this, I would not have worried aobut it and spent time with them, but they were about 9 hours away when I was doing this, so it would have been this or perhaps watching an episode of NCIS.

Etmax
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Re: OSH Park
Etmax   2/26/2014 10:05:16 PM
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I use a service that does 2 x 8"x10" of PCB material for $300 plus shipping. They do 7/7 track & spacing with 8thou vias and 0.2mm annular rings. I just put a dozen or so designs together on the panel. Includes BBT and DRC and I can get gold flash for an additional $50. $300-$350 might sound like a lot but 2 panels of 8"x 10" with as many designs as I want if I do the panelisation myself it's hard to beat for an all inclusive. Comes with both sides silk and mask. At the end of the day we have only so much time. We can always get more money but never more time.

Aeroengineer
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Re: OSH Park
Aeroengineer   2/26/2014 10:12:32 PM
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I appreciate the comment, though with my last 10 projects, I could fit all of them on your board and still have a lot of space left.  I would still be out $200+ on the cost of the boards and I would not have been able to have them produced there because I have parts that require the 6/6 spacing that is offered.

 

I do get the point though that time is precious, but at the same time, it I spent all my time worrying about what I should be doing with my time, I would not have learned many valuable lessons of life by either the failures I had to solve, and hence take more time, or the successes that I have had because I would be worried I might waste my time in failure.  There are costs associated with everything, like right now.  I could be making dinner, showering, sleeping, or enjoying this sharing of differing viewpoints.  All cost time and a lost chance to do something in the moment, but I decided on the last option as it gives me a chance to interact with someone as well as understand a different viewpoint.

 

By the way, which is the service you use.  Always good to know of vendors that others would recommend.

Etmax
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Re: OSH Park
Etmax   2/27/2014 12:06:38 AM
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I agree, they were responsive, credit where it's due.

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