[dorkbotpdx-blabber] Interest in Kapton/Mylar stencils?

Aaron Eiche aaron.eiche at gmail.com
Mon Sep 26 18:16:15 EDT 2011


The technique for applying paste prevents this kind of approach. Basically
you want to apply paste to the whole board all at once. If you have multiple
stencils, you'd need to place each of them, secure each of them, and hope
they don't overlap (which would cause paste thickness differences). Because
of the footprints of various parts, this would be virtually impossible. Any
custom board that has want of a stencil needs a custom stencil.

On Mon, Sep 26, 2011 at 3:10 PM, Huck <dhuckaby at paasda.org> wrote:

> I feel the need to chime in even though I've never touched SMT stuff..
>
> Why not just make a run of some of the most common footprints(dunno
> terminology)...and make like 20 sheets or whatever and do a group-buy
> similar to the PCB order... rather than constantly create'n stencils...
>
> I don't know if parts are so NON-standardized in footprint to disallow
> this...as I'm willfully ignorant ;)  But just seems more logical...they
> could be shared around the Monday Meetings and the like...
>
> --Huck
>
>
> On 09/26/11 3:02 PM, Greg Peek wrote:
>
>> 1. Yes, definitely interested. I ordered stencils when @laen had a
>> source for them. I do less SMT than I would like because of the
>> difficulty / expense of getting stencils made.
>>
>> 2. Usually somewhere around 2x2 inches (SMT Arduino shield or PCB),
>> sometimes as small as 1x1 inches of working area per design (Paul's tiny
>> accelerometer board). I've been know to do more than one design a week,
>> but then I have dry spells of zero for a month. So I would guess an
>> average needing of 1 or 2 stencils a month.
>>
>> 3. I'm willing to pay $5 for a stencil to use with a $20 2x2 inch @laen
>> PCB board. Much more than that for only making 3 boards and I'll just
>> hand apply the paste (as I am now).
>>
>> 4. 3 mil puts down a bit too much paste for fine pitch SMT (QFN).
>> Perhaps there is a way for you (or us, the customer) to scale down the
>> openings for fine pitch? I thought one of the main reasons for using
>> Kapton over Mylar was that it is possible, with the right recipe, to use
>> 2 mil material and get fine holes.
>>
>> Working out a deal with @laen would scale up the volume of stencil
>> orders, increasing the payback for the investment involved (but also the
>> workload). Upside, @laen has to stuff the envelopes.
>>
>>
>>
>> On Mon, Sep 26, 2011 at 2:04 PM, Travis Smith <trav at tnhsmith.net
>> <mailto:trav at tnhsmith.net>> wrote:
>>
>>    Hello all-
>>            As some of you may know, I've been working with ADX in
>>    Portland to
>>    define a process to allow us to burn our own Kapton or Mylar stencils
>> on
>>    their laser cutter.  Progress is going slow, partially because I'm
>>    trying to
>>    use 2 mil Kapton instead of 3 mil to reduce the amount of paste.
>>      Thinking
>>    I'll need to scrap that idea and go to 3 mil like everyone else.
>>            ADX is understandably concerned about the engineering time
>>    they're
>>    spending trying to dial in the right burn parameters and process
>>    definition.
>>    They hope to recuperate these costs in the future by selling their
>>    services
>>    to us when we need stencils.
>>            So, I'm looking for some feedback that I can compile into a
>>    report
>>    to give back to them. If you use stencils in your projects, please
>>    take a
>>    moment to answer the following questions. Feel free to just reply to me
>>    (trav AT tnhsmith DOT net), unless you have a comment on the general
>>    topic.
>>
>>    1. Would you be interested in using a local supplier for your stencils?
>>    2. About how many (or what area) of stencils do you need in a
>>    typical month
>>    (or year)?
>>    3. How much would you be willing to pay? (Ohara RP and Pololu both
>>    charge
>>    ~$25 plus shipping)
>>    4. Any other thoughts/input on obtaining stencils locally?
>>
>>                    Thanks in advance for your time,
>>                            Travis
>>
>>
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