Re: [CAD_CAM_EDM_DRO] Re: Stepper motor speeds

----- Original Message -----
From: <JanRwl@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, November 06, 2002 3:17 PM
Subject: Re: [CAD_CAM_EDM_DRO] Re: Stepper motor speeds


> In a message dated 11/6/2002 10:23:05 AM Central Standard Time,
> antonio-ximenez@... writes:
>
> > How do you make the plated holes ????
> >
>
> This is done BEFORE etching. The holes are ALL drilled first, then the
board
> is "sensitized" in a bath of chemical that makes the ENTIRE surface
> conductive, i.e., the "walls" of the holes, too, electrically-connected to
> the copper on both surfaces. Then the board is ELECTROPLATED in copper.
> Yes, this not only puts copper INSIDE the holes (on the walls of the
holes),
> but it THICKENS the copper surfaces, too. Thus, some (all?) PC-shops use
> "half-ounce" copper, since it gets thickened when "plating-through".
>
> Then, a "negative" image is laid on, so that the exposed copper is the
> "tracks" you want, and then that is "solder-plated" (yes, a tin-lead alloy
is
> actually electro-deposited on the exposed copper).
>
> Then this image-resist is removed, and . . .
>
> Then that is placed in an etchant-bath (I am NOT a PC-manufacturer, so I
am
> not sure, but I THINK they us ammonium persulfate. NOT ferric chloride,
as
> we "one little PC every few weeks" folks use.) This etchant attacks
copper
> just fine but does NOT "eat the solder".
>
> Once the "unwanted" copper is etched away, the boards are "reflowed",
meaning
> HEATED to the melting point of the solder, so that "solder-plating" flows
> nicely over the copper tracks and "rounds over, nicely".
>
> Then, epoxy "solder-mask" and then "silk-screening" showing which
transistor
> goes which way, where, etc.
>
> Sorry, I have NO clue how the process for "multilayer" is done, at least
not
> sufficiently to describe it here!
>
> Lotsa luck! Jan Rowland, Troll
>
Multilayer boards are created the same way except before the initial drill &
plate step mentioned above, the internal layers are etched using the
photoresist, (not the tin solder plate) and then "Prepreg" (thin layers of
epoxy-glass that are partially cured and with no copper) is placed between
the etched layers. After heating in a press, the board is fully cured and
becomes one solid piece. Then the process is exactly as youi describe it
above.
>
> [Non-text portions of this message have been removed]
>
>
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