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FeClЗ,
or we etch the boards.
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(c) VTS'99
So, today I will tell you how you can...
for me to make the coolest printed circuit board,
not inferior to factory ones... from tube times
TVs ;) Although especially persistent and
those who are super careful might even etch themselves
board according to the 4th accuracy class, albeit in
single copy ;)
To begin You need to stock up on materials
lami - ferric chloride (sold on any
radio push, usually in bags, in dry vi-
de - yellow-green powder. Well absorbed -
absorbs moisture, so it’s not completely dry) and
foiled fiberglass laminate (for now
one-sided metallization is enough).
As a result of all our work, we must
make conductive paths from foil,
which will connect the contact pads with
parts soldered to them. Yes, of course
a simple way is to cut with a special knife
press the foil so thatthe remaining isolated
bathtub copper pads were connected accordingly
current conclusions. But for complex boards this
the method is too labor-intensive, and poisoning chlorine
hardware is much more interesting ;) reliable
nah, more beautiful...
So, stage one. Board routing.
It is necessary to develop a printed pattern
conductors. In the simplest cases this is de-
barked manually. At first, try
try to make several board options, with
different arrangement of elements, and selection
rite the best. The selection criterion should be
min board dimensions and min number of jumpers
check.
It is best to trace the board with a pencil
on a checkered piece of paper with a pitch of Smm, because everything
the distances between the terminals are usually multiples
2.Smm (half a cell). For example, pin pitch
microcircuits - 2.Smm, resistor - 1Omm, con-
densator - Smm, etc. Please note
what to manually draw a path between the output-
mi microcircuits are difficult, although over time you
you can etch such jewelry
plots.
Don't forget about the mounting holes and
thickened power conductors: based on
min 1mm per ampere of flowing current. And the earth
lei can fill empty spaces -
this will reduce the level of interference and interference.
And don't forget that printed conductors
are located at the bottom of the board, i.e. it is necessary to use
use mirror display base
wok of microcircuits, transistors, etc.
By the way, you can use
programs like LAYOUT86/91.
Stage two. Preparation of the workpiece and
carrying a protective pattern.
It is most convenient to cut the workpiece but
metal saw. Remove the sandpaper
what a hangnail. You can adjust the dimensions to
file, round the corners.
Next, the foil needs to be degreased and desired
Carefully remove the oxide layer. This can be done-
but like mechanically fine-grained sandpaper,
and chemically - using acetone (spir-
yes, gasoline...) and a weak saline solution
acids respectively.
To transfer a picture you can use
carbon paper (carbon paper). In places where
where should the holes be for the leads?
parts, it is necessary to make indentations
core or awl.
By the way, here we have rumors that
You can transfer a drawing from a printout
grain printer, ironing it with an iron
(directly from P-CAD ;). Although under great question
the acid resistance of such a coating is determined by dew.
Nowdraw paths using glass
linseed resfeder with nitro varnish, tsapon varnish,
asphalt bitumen varnish, BF-2 glue or la-
com for nails (and anything in general -
as long as it is not washed off with water and reacts with
FeCl3 has not entered - check first for
sample). In places where leads are soldered, it is necessary to
I can make contact pads.If not
glass resfeder, can be produced
its analogue from a used rod of a regular one
ballpoint pen. To do this, remove the writing
part, leaving an empty tube. Then in
its middle part is heated over a flame
lighters or matches until the material softens
rial, and stretch. At the same time, in place
heating diameter decreases. Now in this
point the tube is cut with a blade and obtained
there is a resfeder. Of course, from the first time
it probably won't work out, but after a few
attempts, you can get enough quality
vein and thin hole.
By the way, do not forget to select the viscosity
protective paint - so that it does not get stuck
in the refeder, but also so that it is not too
liquid.
Improvements in the pattern are eliminated with sharp
tip of a knife, scalpel or white bladestraight razor after rinse
will dry out.
Stage three. Etching.For etching
a solution of ferric chloride tri-
valence Divalent chloride etch
it won't, so it's not highly recommended
Dry powder can be stored for a long time (a year or more)
FeClЗ - its properties will deteriorate. Go-
it is much safer to store the solution in glass
bottles with good corks.
To obtain a solution density 1.3
you need to dissolve 150g of ferric chloride
in 2OOml of water, preferably distilled,
or at least boiled. Should be dissolved
carefully, because there will be little
sho warming up.
For etching it is necessary to use
porcelain or plastic bath
(for example, photographic), into which you pour
the required amount of solution is added and
the workpiece is lowered.
Etching will occur intensive
no, if the solution is heated to 40-50 degrees
spirits and create its movement, for example,
shake from time to time. In the fresh
solution at room temperature board tra-
curls in half an hour, in stale - up to an hour
about one and a half. When heated - 2-3 times
faster.
Etched board rinse thoroughly
alternating hot and cold flow
water, dry and remove the protective paint with
using a blade, fine sandpaper or solvent
body (which will help).
The last stage. Drilling and tinning. B
the previously designated core locations are drilled from
hole for leads - from 0.8mm for micros
chem up to 1.Smm for powerful resistors. Then
Use fine sandpaper to remove burrs and coverings.
cover the board with rosin varnish (a solution of rosin
foley in alcohol or acetone).
In principle, it is not necessary to tin the board,
but, but it is desirable, because this will protect
conductors from oxidation. Tinning is produced
use a soldering iron with a power of 40-80 W (depending on
depending on the thickness of the conductors). Not worth it
forget that overheating of tracks can cause
remove thempeel.
Instead of a conclusion. Now to the resulting
the board can be soldered into parts - produced
installation. It is recommended to install first
parts so that there is sufficient mechanical
ical strength, and only then solder
them to the contact pads (in production,
for example, according to GOSTs, soldering is prohibited without
mechanicalstrength, because this causes
internal mechanical stresses in
such a strong material like solder).
To do this, it is necessary to
Let's mold the pins of the parts - take a look -
those as done on factory boards.
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