[TriEmbed] OSH Stencil notes

[Brian]

On 11/14/2016 11:26 AM, Pete Soper via TriEmbed wrote:
> I always enjoy your good cents.

Bad cents also included, no extra charge.

> If mylar from Pololu tends to sit flat that would be worth some money.

Mylar from Pololu is shipped in a tube, so it must be flattened before 
use.  Once that's done, it does sit reasonably flat.  Obviously care 
must still be taken.

My flattening methods have been the heavy-book-sandwich as well as using 
magnets to affix it flat to one of my whiteboards (oriented such that 
the curve tendency is convex).  In a warmish room, a couple days oughta 
do it.

Realistically though, a bit of smear and bleed is going to be 
unavoidable unless you're using a machine.  Hopefully your paste has 
good flux and will (literally) pull itself together during reflow. 
Mopping up afterward with more flux and solder wick is very effective. 
Even QFN packages can be de-bridged that way, especially on a board with 
a good soldermask.

SMT is fun!

-B


>
> -Pete
>
> On 11/14/2016 10:00 AM, Brian via TriEmbed wrote:
>> Joining this conversation a bit late, but having ordered stencils in a
>> variety of materials from a variety of vendors, here are my three cents:
>>
>> - OSH Stencils' kapton (polyimide) stencils are the least pleasing to
>> use, IMNSHO.  They are very flimsy and feel quite fragile.
>>
>> - For flexible-substrate stencils, I've had better experiences with
>> mylar stencils from Pololu.  They're a bit more expensive, but I'd say
>> it's worth the extra expense to have a sturdier material.
>>
>> - OSH appears to offer stainless steel at a very competitive price;
>> I've only ever ordered stainless steel from Stencils Unlimited.
>> Stainless is definitely the best stencil to use, in no small part
>> because it is flat and rigid.  I think the premium for metal stencils
>> is well worth it, especially for smaller designs of which you plan to
>> build many.
>>
>> IANAL, YMMV, OMG, WTF, BBQ!
>>
>> -B
>>
>> On 11/09/2016 03:55 PM, Pete Soper via TriEmbed wrote:
>>> I made some notes while listening to an interview of the guy behind OSH
>>> Stencils:
>>>
>>> http://triembed.org/blog/?p=1895 <http://triembed.org/blog/?p=1895>
>>>
>>> By the way, I'm not in the position to publish this at the moment, but
>>> several weeks back I worked out the steps necessary to "combine" Eagle
>>> designs so one board file can be uploaded to OSH Stencils for a
>>> single metal stencil that can be used for the multiple designs. By
>>> having a set of fiduciary marks for each board (and adding a few lines
>>> to the stencil with a permanent marker) it is straight forward to
>>> minimize cost. (What the hell am I babbling about here? The minimum
>>> border size of the metal stencils make them *expensive* for
>>> small designs.) This can no doubt be done with alternative tools like
>>> gerbmerge.
>>>
>>> -Pete
>>>
>>>
>>>
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>>
>>
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>
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