[TriEmbed] TriEmbed Digest, Vol 11, Issue 6

Pete Soper pete at soper.us
Sat Apr 5 17:03:13 CDT 2014


Here are two short treatments of the issue of humidity for those that 
wonder what we're referring to:

http://www.intersil.com/content/dam/Intersil/documents/tb36/tb363.pdf

http://www.eetindia.co.in/STATIC/PDF/200804/EEIOL_2008APR04_MANF_TEST_TA_01.pdf

With some of my parts flagged as humidity-sensitive I don't know if I'll 
use them in a week or a year or three and I have no sense of the actual 
probabilities of popcorn cracking if I leave them sitting in a humid 
basement for six months. But I agree with Martin that this is a relative 
non-issue.  And if a part cracked how would we even know it was that vs 
one of seven other unmeasured and uncontrolled variables?

The Adafruit meter with the SMD tweezer-probes appears to me to have 
better specifications and features in every respect than the Sparkfun one.

As for the lack of part numbers on the SMD caps, the tweezer gadget will 
work for that (until you encounter unmarked SMD inductors, that is), but 
it's hugely easier to keep the components segregated and double check 
yourself as you are picking and placing components. Place one type/value 
at a time rather than switching between containers or tape segments or 
trays as you put parts on board(s).

Simple hand magnifiers work fine for reading part numbers, and, as I 
said, the solution is to stop reading them and just read the label on 
the box/tube/tape. :-)

But as an FYI on this subject, I've decided life is too short for hand 
assembling 0402 parts. I can deal with 0603 well now, but I'm just going 
to pass on the smaller ones and make the boards bigger instead. :-)

-Pete


On 04/04/2014 08:31 PM, Charles McClelland wrote:
> Pete, Carl and All,
>
> Thanks for your advice on this topic.  I wanted to take a look at the components and I have a couple more questions if I can:
>
> - Optics - My magnifying glass is not strong enough to read the marking clearly on the components.  I can make out some of the numbers (like 102 which I assume means 10x10^2 on the 1k resistors) but it is tough.  I know Pete is not satisfied with the USB microscope he got from Adafruit but, what do you all use to inspect these parts?
>
> - Markings - not all the parts even have markings.  The capacitors do not seem to be marked at all leaving me to wonder how I can be sure of the part I am using.  Do I need something like this: https://www.sparkfun.com/products/10829
>
> - Shelf life - According to the markings on the bag, the ATMEGA328 SMD chips need to be installed within 168 hours of opening the bag.  Unless the approach Pete laid out below works, it seems I need to buy these chips as I need them which might get expensive.  The other humidity sensitive part - the LEDs - say they need to be installed within a week.  I had no idea  some of these parts had the shelf life of lettuce.  Is there a local supplier?
>
> Thanks again for putting up with my SMD-newbie questions.
>
> Chip
>
>   
> On Apr 4, 2014, at 6:28 PM, triembed-request at triembed.org wrote:
>
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>> Today's Topics:
>>
>>    1. Surface Mount Components Newbie Questions (Charles McClelland)
>>    2. Fwd:  Surface Mount Components Newbie Questions (Carl Nobile)
>>    3. Re: Surface Mount Components Newbie Questions (Carl Nobile)
>>    4. Re: Surface Mount Components Newbie Questions (Pete Soper)
>>
>>
>> ----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Fri, 4 Apr 2014 16:38:32 -0400
>> From: Charles McClelland <chip at mcclellands.org>
>> To: TriEmbed Discussion <triembed at triembed.org>
>> Subject: [TriEmbed] Surface Mount Components Newbie Questions
>> Message-ID: <9D001F91-9195-4A64-AD0C-B360E3836CEF at mcclellands.org>
>> Content-Type: text/plain; charset=us-ascii
>>
>> Hey all,
>>
>> I am gearing up for my first surface mount project.  OSH Park has just told me the boards are in the mail and DigiKey just sent me the bill of materials.  I have some questions now that I have opened the box from DigiKey:
>>
>> 1) Some of the components claim to be humidity sensitive.  Is this a big deal for hobby use?  Do I need to keep these in a sealed bag with desiccant or is that overkill?
>>
>> 2) Some of the components claim to be sensitive to electrostatic discharge.  I have yet to fry a through hold component - are surface mount components more sensitive?
>>
>> 3) The components come on tape which will be inefficient to store using the cool storage boxes Pete showed me.  Is there anything wrong with removing the parts from the tape?
>>
>> I went with 0805 components so nothing is microscopic.
>>
>> Thanks,
>>
>> Chip
>>
>>
>>
>>
>>
>> ------------------------------
>>
>> Message: 2
>> Date: Fri, 4 Apr 2014 16:55:57 -0400
>> From: Carl Nobile <carl.nobile at gmail.com>
>> To: TriEmbed <TriEmbed at triembed.org>
>> Subject: [TriEmbed] Fwd:  Surface Mount Components Newbie Questions
>> Message-ID:
>> 	<CAGQqDQKgkOYCM0U6sC7ynUsT6ykGEVjX6wz=eh71CFDLDkEU2g at mail.gmail.com>
>> Content-Type: text/plain; charset="utf-8"
>>
>> Sorry I sent this to Chip and forgot to click all.
>>
>> Chip,
>>
>> The static issue is the one to be very careful about. If you walk on a
>> staticky rug then touch a component, say good by to the component. At the
>> point where you can feel a shock it is already way too high and will blow
>> any static sensitive component. They must be kept in one of those dark gray
>> static bags. DO NOT use the pink ones, they're useless.
>>
>> BTW, components do not know if you are a hobbyist or a professional, if the
>> component doesn't like the humidity it will be damaged in either case.
>>
>> I always keep most parts in sealed plastic bags. If static electricity is
>> not an issue, like with resistors and capacitors, you can use clear plastic
>> bags. I get them at hobby stores, they come in all the right sizes and are
>> pretty cheap.
>>
>> Carl
>>
>>
>>
>> On Fri, Apr 4, 2014 at 4:38 PM, Charles McClelland <chip at mcclellands.org>wrote:
>>
>>> Hey all,
>>>
>>> I am gearing up for my first surface mount project.  OSH Park has just
>>> told me the boards are in the mail and DigiKey just sent me the bill of
>>> materials.  I have some questions now that I have opened the box from
>>> DigiKey:
>>>
>>> 1) Some of the components claim to be humidity sensitive.  Is this a big
>>> deal for hobby use?  Do I need to keep these in a sealed bag with desiccant
>>> or is that overkill?
>>>
>>> 2) Some of the components claim to be sensitive to electrostatic
>>> discharge.  I have yet to fry a through hold component - are surface mount
>>> components more sensitive?
>>>
>>> 3) The components come on tape which will be inefficient to store using
>>> the cool storage boxes Pete showed me.  Is there anything wrong with
>>> removing the parts from the tape?
>>>
>>> I went with 0805 components so nothing is microscopic.
>>>
>>> Thanks,
>>>
>>> Chip
>>>
>>>
>>>
>>> _______________________________________________
>>> Triangle, NC Embedded Computing mailing list
>>> TriEmbed at triembed.org
>>> http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
>>> TriEmbed web site: http://TriEmbed.org
>>>
>>
>>
>> -- 
>> -------------------------------------------------------------------------------
>> Carl J. Nobile (Software Engineer)
>> carl.nobile at gmail.com
>> -------------------------------------------------------------------------------
>>
>>
>>
>>
>> -- 
>> -------------------------------------------------------------------------------
>> Carl J. Nobile (Software Engineer)
>> carl.nobile at gmail.com
>> -------------------------------------------------------------------------------
>> -------------- next part --------------
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>> ------------------------------
>>
>> Message: 3
>> Date: Fri, 4 Apr 2014 17:31:48 -0400
>> From: Carl Nobile <carl.nobile at gmail.com>
>> To: Charles McClelland <chip at mcclellands.org>, TriEmbed
>> 	<TriEmbed at triembed.org>
>> Subject: Re: [TriEmbed] Surface Mount Components Newbie Questions
>> Message-ID:
>> 	<CAGQqDQ+8g=uXYw7s-9pgBBMcwZ66Fp7y4ZFNs0UV0gBFGUWfpA at mail.gmail.com>
>> Content-Type: text/plain; charset="utf-8"
>>
>> Chip,
>>
>> You have a point about the automated machines, if the humidity is high the
>> machines may malfunction. However, I do know of components that have
>> humidity issues also like some capacitors. It is not the water itself
>> which, by-the-way, will not conduct electricity, it's the impurities in the
>> water that is the issue. Humidity can change a crystal's frequency. When I
>> used to work on transmitters the oscillators were put into a heated box so
>> the radio/TV station would not drift off frequency. An FCC pink slip would
>> show up in the stations mail box with a hefty fine attached if the station
>> frequency did drift.
>>
>> I usually leave the parts on the ribbon tape and fold them up and put them
>> in a bag. Too much work taking them all apart and getting them mixed up
>> with other like parts.
>>
>> Carl
>>
>>
>>
>> On Fri, Apr 4, 2014 at 5:14 PM, Charles McClelland <chip at mcclellands.org>wrote:
>>
>>> Carl,
>>>
>>> Thanks, I guess I do need to think about static.  I also like you plastic
>>> bag idea.
>>>
>>> On your point about hobbits or professional, let me explain what I was
>>> thinking.   I assume that the reason many of these components are sold as
>>> cut tape is to accommodate the hobbyist who wants to order just a few.
>>> However, I am assuming that these same components are sold in entire reels
>>> of tape to the professional who might use an automated machine to place
>>> them on a board as part of a production line process.  I guess I was
>>> wondering if it was the performance of these components in one of these
>>> automated production lines where humidity is an issue.  Otherwise, will
>>> that sensitivity to humidity be an issue for the component on the assembled
>>> board?
>>>
>>> Thanks,
>>>
>>> Chip
>>>
>>>
>>> On Apr 4, 2014, at 4:51 PM, Carl Nobile <carl.nobile at gmail.com> wrote:
>>>
>>> Chip,
>>>
>>> The static issue is the one to be very careful about. If you walk on a
>>> staticky rug then touch a component, say good by to the component. At the
>>> point where you can feel a shock it is already way too high and will blow
>>> any static sensitive component. They must be kept in one of those dark gray
>>> static bags. DO NOT use the pink ones, they're useless.
>>>
>>> BTW, components do not know if you are a hobbyist or a professional, if
>>> the component doesn't like the humidity it will be damaged in either case.
>>>
>>> I always keep most parts in sealed plastic bags. If static electricity is
>>> not an issue, like with resistors and capacitors, you can use clear plastic
>>> bags. I get them at hobby stores, they come in all the right sizes and are
>>> pretty cheap.
>>>
>>> Carl
>>>
>>>
>>>
>>> On Fri, Apr 4, 2014 at 4:38 PM, Charles McClelland <chip at mcclellands.org>wrote:
>>>
>>>> Hey all,
>>>>
>>>> I am gearing up for my first surface mount project.  OSH Park has just
>>>> told me the boards are in the mail and DigiKey just sent me the bill of
>>>> materials.  I have some questions now that I have opened the box from
>>>> DigiKey:
>>>>
>>>> 1) Some of the components claim to be humidity sensitive.  Is this a big
>>>> deal for hobby use?  Do I need to keep these in a sealed bag with desiccant
>>>> or is that overkill?
>>>>
>>>> 2) Some of the components claim to be sensitive to electrostatic
>>>> discharge.  I have yet to fry a through hold component - are surface mount
>>>> components more sensitive?
>>>>
>>>> 3) The components come on tape which will be inefficient to store using
>>>> the cool storage boxes Pete showed me.  Is there anything wrong with
>>>> removing the parts from the tape?
>>>>
>>>> I went with 0805 components so nothing is microscopic.
>>>>
>>>> Thanks,
>>>>
>>>> Chip
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> Triangle, NC Embedded Computing mailing list
>>>> TriEmbed at triembed.org
>>>> http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
>>>> TriEmbed web site: http://TriEmbed.org <http://triembed.org/>
>>>>
>>>
>>>
>>> --
>>>
>>> -------------------------------------------------------------------------------
>>> Carl J. Nobile (Software Engineer)
>>> carl.nobile at gmail.com
>>> -------------------------------------------------------------------------------
>>>
>>>
>>>
>>>
>>
>> -- 
>> -------------------------------------------------------------------------------
>> Carl J. Nobile (Software Engineer)
>> carl.nobile at gmail.com
>> -------------------------------------------------------------------------------
>> -------------- next part --------------
>> An HTML attachment was scrubbed...
>> URL: <http://mail.triembed.org/pipermail/triembed_triembed.org/attachments/20140404/b42fbaee/attachment-0001.html>
>>
>> ------------------------------
>>
>> Message: 4
>> Date: Fri, 04 Apr 2014 18:28:33 -0400
>> From: Pete Soper <pete at soper.us>
>> To: triembed at triembed.org
>> Subject: Re: [TriEmbed] Surface Mount Components Newbie Questions
>> Message-ID: <533F3211.8000906 at soper.us>
>> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>>
>> I leave those chips in their bags. Inside with the chips are bags of
>> desiccants. I'm told that the basic issue is that if the chip absorbs
>> much moisture then when it goes through the reflow oven it can
>> "popcorn." I don't need to describe what that means. I leave chips like
>> this in the bags, then when I'm going to use a fraction of them I put
>> the remainder with the desiccant bags into airtight containers with the
>> humidity test strips. This may be overkill.
>>
>> And as I type this I'm about to test out the low tech hood and vent
>> system for my oven. This is a very small oven and I have a very powerful
>> fan pushing air out of the basement, so hopefully I won't have to run
>> the oven outdoors in the near future.
>> -Pete
>>
>> On 04/04/2014 04:38 PM, Charles McClelland wrote:
>>> Hey all,
>>>
>>> I am gearing up for my first surface mount project.  OSH Park has just told me the boards are in the mail and DigiKey just sent me the bill of materials.  I have some questions now that I have opened the box from DigiKey:
>>>
>>> 1) Some of the components claim to be humidity sensitive.  Is this a big deal for hobby use?  Do I need to keep these in a sealed bag with desiccant or is that overkill?
>>>
>>> 2) Some of the components claim to be sensitive to electrostatic discharge.  I have yet to fry a through hold component - are surface mount components more sensitive?
>>>
>>> 3) The components come on tape which will be inefficient to store using the cool storage boxes Pete showed me.  Is there anything wrong with removing the parts from the tape?
>>>
>>> I went with 0805 components so nothing is microscopic.
>>>
>>> Thanks,
>>>
>>> Chip
>>>
>>>
>>>
>>> _______________________________________________
>>> Triangle, NC Embedded Computing mailing list
>>> TriEmbed at triembed.org
>>> http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
>>> TriEmbed web site: http://TriEmbed.org
>>
>>
>>
>> ------------------------------
>>
>> Subject: Digest Footer
>>
>> _______________________________________________
>> TriEmbed mailing list
>> TriEmbed at triembed.org
>> http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
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>>
>> ------------------------------
>>
>> End of TriEmbed Digest, Vol 11, Issue 6
>> ***************************************
>
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