Gift to

Description
a) Print frame (same as for nega tive)
.b) NO. 2 Photoflood bulb
c) Metal developing tray (cake pan,
etc.)
d) Blank PC boards sensitized with
Kodak KPR·4
e) Kepro Type KD Developer
Tab le 5. Equipment and materials for board expos ure and
develop ing.
rever sed from the pattern
actua ll y required as you
look at it in this attitude.
Clamp th e print fr am e
pieces securely to fo rce the
positive and f ilm ti ghtly
together.
Next . pla ce the pr int
fram e over the "w indow" in
your exposure box with the
positi ve side do wn . N ow
the positi ve artw ork w ill be
between th e fi Im and the
li ght source. Either cover
the ext ra pieces of f ilm you
cut ou t earl ier or place a
heavy to we l or equi valent
over the whole exposure
bo x-print fr ame assembly
and yo u' re ready to take the
picture . Press the butt on on
the exposure box and ho ld
it down for one seco nd. Remove
the fi lm fr om the
fra me and cli p one corner
off to indicate yo ur f irst expo
sure. Cov er t he fi lm up
and reload the f ram e with
another piece. Expose it as
above exce pt mak e the exposure
time Vl secon d this
time.
Remove you r second exposure
from the frame and
cl ip two co rners off to mark
it; then cove r it up. Make a
fin al exposure w it h the button
pressed and released
abou t as fast as you can.
Cl ip three corners off thi s
pie ce and t hen devel op all
three exposures together as
follows:
1. Place the film, emulsio
n side dow n, in the
devel oper for a second or
two. Next, turn it over and
agit at e for about ten seconds.
Push the fi lm to the
bottom of th e tr ay and
leave it for 21;2 minu tes.
(Hand le t he fil m by the
edges at all times.)
2. Remove t he film from
110 73 Magazine· Oct ober, 1980
Source
Home brew
Photo Store
Dept. Store
Kepro
Kepro
the developer. all ow ing excess
li quid to dr ain off in
the tr ay, then transfer t he
fi lm to the stop ba th.
Agitate it in th e bath for
about 30 seconds.
3. Remove th e f ilm fr om
the stop bath, draining the
excess, and place it in the
fixe r tray. Leave it in the fixer
for abo ut three minutes,
agitat ing period ically.
4. Remove th e f il m fr om
the f ixer and pl ace it under
runni ng water for 20 to 30
minutes. Ordin ary room
lights may be turned on
after removal fr om th e f ixer.
5. Dry the f ilm wi th a
squeegee and hang it up
w it h film cl ips or clothespi
ns to dry complet ely.
You should actuall y see
the pattern ima ge on film
shor tly af ter beginnin g Step
No . 1. It w ill appear w hite
on a dark backg rou nd. After
a few seconds of agitation
in the f ixer, howeve r, it
should seem to di sappear.
Holding it up to the safelig
ht wi ll revea l that t he
white areas have act ually
turned cle ar on a b lack
bac kground.
The shortest exposure
probabl y wi ll turn out to be
the best of the three. Examine
them all caref ully,
thou gh, as you should be
able to see some effects of
exposure time.
After th orough dr ying,
the negative is complete
and m ay be used to expose
PC bo ards to produce the
pattern as ma ny times as is
desired .
Board Exposure and
Developing
This fi nal step, the equ ipme
nt and mate rial s for
wh ich are li sted in Table 5,
is the simplest of all. However,
si nce th e bo a rd
m aterial , unlike ou r li th o
fil m, is ex pensive, yo u
should take a little extra
care to avoid ruin ing a
board . Ab ou t th e bigge st
danger is that you may inadverte
ntly expose the
photosensitized surface to
too much light before the
negative is in place. Fortun
ately , they are sensitive
to ult ravi olet light; sub dued
ambient li ght will no t ruin
them . The Kepro instructi
on s call f or a 15- or
25-Wa tt incand escent (not
fluorescent ) bulb at least
seven feet away and shaded
from your wo rk area when
setting up the bo ard for expo
sure. They also say the
red safelight is sat isfactory,
but I've not tried thi s.
To conti nue, you wou ld
do wel l to ta ke on e 4" X 6"
boa rd fr om the light-t ight
package and, under proper
ligh t ing c o n d it io n s, as
above , cut it into pieces
w hi ch w ill fi t your pr e­
v io us ly- ob ta i ned test
negative. Place a piece of
sensitized board in your
print frame w it h the copper
side up. For t his and all subsequent
opera tions, handl e
t he board on ly by its edges.
Nex t, position the negati
ve on top of th e PC boa rd
w ith the pattern show ing as
yo u want the board to look
(i.e., mak e sure it isn't
reversed). Take some pa ins
to align the negat ive correctly,
using your reg ist rati
on marks. Press the board
and n eg a t i v e f i r m l y
together by cl ampin g th e
print fr ame closed.
Expo se th e bo ard using a
#2 photoflood bulb about
12 inches away f rom the
print fram e for about five to
six mi nute s. The exposure
tim e here is not critical.
Next, pu t th e board copper
side up in a metal tray w ith
abo ut y, inch of developer.
Leave it in the developer for
three minutes, with pe riodic
agitation.
Rem ove t he board from
the developi ng solution and
rinse it well under running
wa ter for a mi nute or two. A
sink sp ray attac hmen t
works we ll for this . Not e
th at after being in t he
dev elo per f o r the prescribed
time, the bo ard is
no longer light sensitive.
After rin si ng , ho ld t he
boa rd at an angle to the
room lighting and your pattern
sho uld be visible as a
texture difference on the
board surface.
The final step is to let the
boa rd dry ove rnig ht or in a
warm (150°) ov en for abo ut
five minutes. As me ntio ned
before, avoid touching the
copper surface at any tim e.
Prior to drying, the resist
pa ttern is soft and can be
damage d. A lso, the other
areas of the board wi ll not
respond as well to t he acid
bath during etching if oi ls
fr,om your fingers are on it.
Board Etching
After the drying step, yo u
may proce ed to etc h the
boa rd as you wo ul d with
t he di rect-resist method.
Place it in a pl astic tr ay wi th
about y, inch of the fe rric
chlor ide et chant solution.
Agita te th e t ra y during
etchi ng to speed up the process.
Also, if you can raise
the temperature of t he bath
to about 100° F, t he time req
uired will be reduced.
D ep e n d in g upon t h e
a moun t of ag ita t io n,
temp era ture, and how fresh
the etc hant is, t he etching
pro c e ss shou l d tak e
roughly 30 minutes to one
ho ur.
After all unwanted copper
has been etc hed away,
remove the bo ard fr om the
tray and rinse it we ll under
runni ng water for tw o or
three mi nutes to stop the
chem ica l reaction . Then,
using fine stee l w o ol ,
rem ove the resist from the
copper pattern. Now drill
your lead holes and th e job
is done.
Troubleshoo ting
A s mentio ned seve ra l