[TriEmbed] OSH Stencil notes

[Pete Soper]

I haven't noticed any tendency for kapton/polyamide stencils to lose 
their curvature, even after a year or more. For fun I clamped one 
between two sheets of metal with a vise and brought the whole thing up 
to about 170F and held that for a few hours. and then sat it outside to 
cool. When the stencil came back out it was exactly the same shape: a 
little arc of roughly two inch radius waiting to be annoying once again. 
So mylar is better than kapton on this score too.
-Pete


On 11/14/2016 12:02 PM, Brian via TriEmbed wrote:
> 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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>
>
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