.... now back to design considerations!
"....with your technique, even the smallest, requires a complete redo. I can change an R in a minute while you have a 4 hr turn around" -Derk
I hear you, Yes! but my rational is this:
Your capability to change out a resistor in one minute is a "red herring" to the "means-to-an-end" that my assembly affords.
Think about the amount of time you had invested into fabricating your prototype before you had a "resistor" to replace!
Compare your "conventional methods" to the fabrication of my current project.
Build a working "proof-of concept" device on a 1.5" x 3/4" multi-layer(5 layer) PCB for field testing outdoors(wet environment) with two 64 pin QFN ICs with around 40 0404 discretes.
I could do this in 4 hrs, every 4 hrs, you would need at least a month (and thats assuming you have the special equipment to fabricate such a complex micro-sized assembly ... most "homebrewers" don't)
And this is a "real" project, its an "invisible fence" (pet containment) and is embedded into a dog's collar.
--- In Homebrew_PCBs@yahoogroups.com, "Richard" <richard.liberatoscioli@...> wrote:
>
> Hi Derk!
>
> Thank-you for your added/expanded thoughts here.
>
> In this most resent iteration, I do now hold with much more in what your presenting. I now have a much better understanding to your points of view.
>
> This concept assembly proposal is certainly not the cure all for all situations.
>
> I venture in this concept to address the desire to "homebrew" the many mobile projects I have in mind using the absolutely awesome capabilities of these new generation microchips, but realizing the "micro size" nature of them threatens the affordability and capability of the "homebrewers" to fabracate them.
>
> This is my quest.
>
>
>
>
> --- In Homebrew_PCBs@yahoogroups.com, Derk Steggewentz <derks@> wrote:
> >
> > Richard wrote:
> > >
> > >
> > >
> > > Excellent and very powerful PCB CAD software already
> > > exists(KICAD,Eagle,etc.)for FREE! Do you really want to start your
> > > project with trying to first write your own routing software?? I don't
> > > think the "homebrewer" has on staff a seasoned team of code writers at
> > > their disposal : (
> > >
> > No, I don't want to reinvent and reimplement existing router apps. I am
> > thinking of using the scan to e.g correct component placement in the
> > input file of the Router, using maybe a router produced Gerber and
> > slightly shifting components, modifying/extending Kicad etc. etc. There
> > are many approaches thinkable and they don't seem insurmountable to me.
> >
> >
> >
> >
> > > Well, yes it does! The CAD software un-forgivenly demands this. It
> > > expects what you place in its "virtual design board" to be absolutely
> > > representative of the real world "outside physical placement" of the
> > > actual components location. When I have you print the component layout
> > > screen to the substrate, the CAD software later makes reference to
> > > this fine placement when you flip the module upside down and now needs
> > > to print micro thin conductive traces. Think about a 128 pin QFN IC
> > > with lets say 50 0404 SMDs. Your SMDs better be right on the money!
> > >
> > That problem is exactly what I tried to solve with my suggestion. Did
> > you ever try to manually place something onto something adhesive? When I
> > do, it's usually always a tiny little bit off. And then there is no
> > pushing around anymore and cursing won't help either, as soon as one
> > corner touches the adhesive surface, that's it. Well, I guess some
> > mechanical and optical (think parallax) help can be constructed. I'd
> > rather write some code, trying to take human failure out of the equation.
> >
> > > In re of "probing" .... your wrong! All the SMDs remain
> > > 100%accessible, even the connections "inside" of the constructed
> > > "micro-hybrids". Yes, they are covered by the insulating mask, simply
> > > run your finished module through the printer again, this time printing
> > > the "inverted version" of the component screen. With a micro-sized
> > > drill or sharp needle point probe, slightly tag the surface to pass
> > > through to the conductive layer underneat
> > >
> > I like your idea of 'running your finished module through the printer
> > again, this time printing the "inverted version" of the component
> > screen'. Good thought. But I have difficulties to think of how that
> > would work in the real world. What is if there is a conductive layer in
> > between, e.g. a ground plane, which I can imagine you want considering
> > all this tight spacing and possibilities of capacitive coupling etc? Or,
> > if no layer, what if a trace crosses just there and you are poking your
> > needle through possibly more then one of them? It doesn't seem practical.
> >
> > >
> > > That's very true! But think about it. Is the "homebrewer" equipped
> > > with special and very expensive "solder re-work stations" that allows
> > > changing out a 128 pin QFN or 0404 SMDs??? Your talking about ICs that
> > > cost on average $3 to $5 and descretes around 20 cents a piece.
> > > Have you ever tried to "solder wick" out a defective IC before?
> > > Chances are you'll lift every "pad" right of the board!
> > > My point is .... for the cost and time involved,if you have a
> > > defective module...PRINT OUT A NEW ONE!! In about 4 hours, your back
> > > up and running.
> > >
> >
> > Yes, I hand solder surface mount components quite frequently. And yes, I
> > have tried and succeeded to "solder wick" out a defective IC before,
> > more then once. O.k. not a 128 pin QFN, but regular SOPs etc.. The
> > majority of SMT components ain't 128 pin QFN's anyway. Regular solder
> > station and a fine tip is all you need. I want to be able to do that
> > with my prototypes where an IC (your quote) 'cost on average $3 to $5'.
> > PRINT OUT A NEW ONE (your quote) and throwing away maybe 10 of the other
> > chips in the circuit worth $3 to $5 apiece does not sound like a great
> > option to me.
> >
> >
> > > Manufacturers today must commit their prototypes to the fabracation of
> > > "real" sized PCBs to even develop the circuitry through many ite
> > > ations of the "true sized" PCBs.
> > >
> > Very true. But that's not what you are doing with your technique. Your
> > 'hybrid' is as far away from a a 'real' sized PCB as it gets.
> >
> > The advantage of real prototype PCBs are also that I can put my finger
> > onto components or traces, introducing capacitance and changing circuit
> > behaviour, take a soldering iron and quickly add a cap, change an R etc
> > etc (with my cheap soldering iron), until i am ready for the next
> > iteration of the prototype pcb.That would possibly save substantially on
> > the number of iterations. Each iteration with your technique, even the
> > smallest, requires a complete redo. I can change an R in a minute while
> > you have a 4 hr turn around.
> >
> > Derk
> >
>