Sourcing a UV Exposure Box for PCB
Development.
-----------------------------------------------
0.
Introduction
1. What's For Sale?
2. Ultraviolet exposure unit with timer
202E
3. Ultraviolet exposure unit with timer 202E - Starter Kit
4. UV
tubes available on eBay
5. Flight case style enclosures
6. Minimum parts
required
7. Conclusion
8. More
9. Developer Crystals - Rapid
34-0395
10. Immerse Tin Crystals - Rapid 34-0775
11. Copper Etchant -
Rapid 87-0722
12. Chemical Storage Requirements
13. Processing Tray Areas
cm'3
0. Introduction
---------------
I wish to start developing
PCBs using the Photoresist and UV Development method. In the past I have
used a Dalo pen and drawn everything out, using ferric cloride to etch the
copper off. I would like to design more complex circuits on a PC and print
to transparancies.
The immiediate requirement is to source a UV
Development box. There are two options; Build One; Buy One. When
considering building one the light output has to be in the range of 400nM.
There is absolutely no point in approaching DIY outlets as they have haven't a
clue what you're talking about (I've been out hunting today). Blacklight
dark UV tubes for making your white t-shirt glow are NOT suitable.
UV
LEDs have been suggested as a possibility. These would need to be of a
high candle output documented to be in the region of 5000-7000mcd, these can
only be economically sourced from Hong Kong. There is a documented concern
that UV LEDs placed in a grid fashion will result in exposure hot spots on the
resulting PCBs. The projects are documented on the net, yet there are no
examples of the PCBs which have been produced. This is a natural concern
despite excitement in using such devices. It would be brilliant to have a
compact UV light box.
1. What's For
Sale?
-------------------
There are very few UV boxes out there. The
most basic are about £120 all in, ranging to £1000's for double sided vaccum
models.
There are very many UV tubes for sale on eBay. UV LEDs are
also available.
2. Ultraviolet exposure unit with timer
202E
--------------------------------------------
This is sold by Rapid
for £115.68 (£98.39+VAT) item number 34-0700. It is also sold by Maplin
for £105.14 (inc. VAT) item number YA36P. It uses a 6-minute mechanical
timer. It uses two 8W 12" (304mm) tubes, 15" maybe??. The exposure
area is 240 x 165mm (9.5 x 9.5"). The overall unit dimensions are 438 x
184 x 102mm (17 x 7 x 4").
http://www.rapidonline.com/productinfo.aspx?tier1=Tools%2c+Fasteners+%26+Production+Equipment&tier2=PCB+Equipment&tier3=Accessories&tier4=Ultraviolet+exposure+unit+with+timer&moduleno=29468
http://www.maplin.co.uk/Search.aspx?criteria=YA36P&DOY=7m4
3. Ultraviolet exposure unit with timer 202E -
Starter
Kit
----------------------------------------------------------
This is
available from Rapid for £129.54 (£110.25+VAT) item number 34-0690. It
includes a number of accessories making a saving of about £20 if bought
seperately. It is Kit B.
These accessories
are;
Rapid Quantity
Description
Unit Sub
(inc.VAT)
----- --------
-----------
---- ---
---------
34-0796
(1) Artwork Drafting
Pack
£4.95
£4.95
(6) Assorted Sheet
Transfer
-----
34-0105
(3) 100 x 160mm SS Photo
PCB £2.49
£7.47
34-0115
(1) 203 x 114mm SS Photo
PCB £3.49
£3.49
34-0295
(1) Polifix
Block
£1.95 £1.95
34-0745
(1) Polypropylene Chemical Tray
-----
34-0395
(2) Developer
Crystals
£0.79 £1.58
34-0385
(1) Seno GS Etching
Kit
£8.95
£8.95
========
£28.39
(£33.36)
========
34-0700
(1) UV Exposure Unit -
202E
£98.39
(£115.68)
========
£126.78
(£148.97)
========
A saving of some £20 is made as predicted. When offset
against the standalone cost of a 202E, the above items are provided for an
imaginary cost of some £10.
4. UV tubes available on
eBay
-----------------------------
A wide range of UV tubes are
available. Most are marketed for use with Fly Killer devices and for
curing Acrylic Nails in beauty salons.
4W 6" (152mm) straight
tubes;
http://cgi.ebay.co.uk/UV-Fluorescent-Tubes-for-Fly-Killers-4w-6_W0QQitemZ260104226984QQcategoryZ72361QQrdZ1QQcmdZViewItem
9W 6" (152mm) nail curing double tubes;
http://cgi.ebay.co.uk/4-pcs-x-9-Watt-Bulk-Tube-For-9W-36W-UV-Nail-Lamp-Dryer_W0QQitemZ220098117777QQcategoryZ67653QQrdZ1QQcmdZViewItem
25W 9" (229mm) U tubes;
http://cgi.ebay.co.uk/UV-Fluorescent-Tubes-for-Fly-Killers-25w-9-U-tube_W0QQitemZ260104226614QQcategoryZ72361QQrdZ1QQcmdZViewItem
22W 8" (203mm) Circular tubes;
http://cgi.ebay.co.uk/Replacement-UV-Tube-for-Electric-Fly-Killer-Circluar_W0QQitemZ320099011789QQcategoryZ72361QQrdZ1QQcmdZViewItem
5. Flight case style
enclosures
-------------------------------
It would be intended to fit a
self build unit into a small flight case. These are relatively expensive
to buy. I have a small case here which is 283 x 235 x 90 (11" x 9" x 3.5")
external dimensions, it was purchased for £9.99 and contains a hobby
drill. It seems that to obtain the smaller flight cases it is economically
easier to buy something else and to use it's presentation case, thus discarding
it's contents. Makeup boxes, hairdryers, all sorts of low priced items
come in perfectly adequate aluminium flight cases.
My full size budget
flight case which can be bought for £11 in a local DIY store has external
dimensions of; 464 x 328 x 150mm (18 x 13 x 6"). It is made as cheaply as
possible yet you could not achieve that level of build yourself without
significant outlay.
6. Minimum parts
required
-------------------------
This is assuming use of a full size
budget flight case, with basic ON/OFF
operation;
Quantity
Description
Unit Sub
(inc.VAT)
--------
-----------
---- ---
---------
(1) Flight
case
£11.00
£11.00
(4) 12" UV
tubes
£5.00
£20.00
(4)
Starters
£1.00
£4.00
(2)
Ballasts
£7.50
£15.00
(1) Rocker ON/OFF
Switch
£1.00
£1.00
(1) IEC 3-pin
socket
£2.00
£2.00
(1) 4mm Cut glass
(local)
£5.00
£5.00
(1) Other unknowns (fixings etc.) £20.00
£20.00
(1) Travelling
costs
£15.00
£15.00
========
£93.00
(NA)
========
The above does not take into consideration PCBs, developer
etc. It appears cost effective to buy the UV 202E kit from Rapid for an
approximate £35 extra. The above also does not take into account stress
and rushing about. I could have the kit on this coming Tuesday after the
Easter bank holiday
weekend.
7.
Conclusion
-------------
It will
be more practical and straightforward to buy the complete kit for £129.54
(£110.25+VAT) item number 34-0690, from Rapid. At this early stage in my
experiences with UV development it makes sense to buy a prepared kit with
instructions where it is all there for you from the moment go.
Having
spoken to my Mother who knows everything her comment is, "You're just like your
bloody Grandfather, you'd lick a farthing out of a turd." In other words,
buy the kit.
8. More
-------
RD WIDE MOUTH BOTTLE 250ML (HD)
(RE)
14-2014 (2)
£0.42 £0.42
RD WIDE MOUTH BOTTLE 100ML (HD)
(RE)
14-2012 (2)
£0.40 £0.40
PHOTOETCH PCB SS 100 X 160
(RC)
34-0105 (3)
£2.49 £7.47
PHOTOETCH PCB DS 100 X 160
(RC)
34-0125 (1)
£2.95 £2.95
POLIFIX BLOCK
(RE)
34-0295 (1)
£1.95 £1.95
JETSTAR A4 10 SHEET PACK
(RE)
39-0780 (1)
£5.50 £5.50
GREEN FILL LAB THERM -10/110
(150MM)(RE) 85-2652
(1) £0.95
£0.95
IMMERSE TIN CRYSTALS
(RE)
34-0775
(1) £12.65
£12.65
DEVELOPER CRYSTALS
(RE)
34-0395 (2)
£0.79 £0.79
9. Developer Crystals -
Rapid 34-0395
-------------------------------------
"Fotoboard (1) and FPC
16 (1) - Mix the powder with hot tap water (50'C) until all the crystals have
disolved at the rate of 50g per litre. Allow solution to cool down and use
between 20'C - 25'C.
Fotoboard (1) and FPC 16 (1) - If the above
concentrations are used the resist will develop very quickly. Do not
over-develop. Normally no more than 30 seconds is needed when the board
should be rinsed immiediately. Above concentrations can also be reduced by
up to a half for longer developing time therefore greater safety margins.
However reducing developer strength may result in the solution having a short
working life.
* Available either in dry crystalline form, sufficient to
produce 500ml solution (1 litre when used with Fotoboard 2), or as 1 litre of
concentrate, to make 10 litres of working solution (20 litres when used with
Fotoboard 2)
* Developer gives a long tank life and fast developing time
*
The shelf life of the solution is considerably greater than the crystalline form
and should be kept in undiluted form in an airtight container
* Safe to use:
contains no sodium hydroxide
* Suitable for use in our tanks 34-0764 and
34-0765"
My crystals we have here are sufficiant to make 1 litre of
solution for use with the Fotoboard 2 which we are using. The weight of a
single packet is 25 grams. Disolve in hot water at a temperature of 50'C,
allow to return to room
temperature;
Weight
Fotoboard (1) Fotoboard
(2)
------
-------------
-------------
25g ....500ml....
...1000ml....
12.5g
....250ml....
....500ml....
10g ....200ml....
....400ml....
7.5g ....150ml....
....300ml....
5g ....100ml.... ....200ml....
10. Immerse
Tin Crystals - Rapid 34-0775
----------------------------------------
"90
grams makes 1 litre - Fill the container containing the powder with hot tap
water (50'C). Replace the top and shake thoroughly to ensure all the
powder has dissolved. Allow solution to cool down to room temperature when
it will be ready for use. Thoroughly scrub clean then rinse copper
surface. Immerse board in solution for 15-30 mins. Remove and wash
thoroughly firstly in cold water then hot. Finally dry with tissues or
paper towels. Mixed solution should be stored in an airtight container or
PCB processing tank with a lid.
* Powder is mixed with warm 50°C water,
allowed to cool and used at room temperature
* No heated tanks are
required
* Low operating temperature allows very small tin molecules to be
deposited, giving a very smooth and hard surface
* The longer the board is
left immersed, the thicker the deposit
* 1.5 to 2.0 microns in 30 minutes and
4.5 microns in up to 2 hours
* Solution will last up to six months, unmixed
powder has unlimited shelf life
* Available in 90g (1 litre) or 450g (5
litres) packs
* Sufficient to cover 0.6m² or 2.7m² of boards"
We need
to make up only the solution that is required. We have 90 grams of
crystals. A 90 gram container costs £13.28
inclusive;
Weight Solution
Cost
------
-------------
------
90g
...1000ml....
£13.28
45g
....500ml....
£6.64
22.5g
....250ml....
£3.32
11.5g
....125ml....
£1.66
10g
....110ml....
£1.48
5g .....55ml....
£0.74
4.5g
.....50ml.... £0.66
11. Copper Etchant - Rapid
87-0722
----------------------------------
"Disolve the crystals in 250ml
of warm water in a plastic or glass vessel, or in an etching tank. Stir to
dissolve and agitate flow of solution over board being etched. Solution
can be re-used and as it becomes weaker heating will increase it's life.
Contents are sufficient for a total amount of 500ml (1 pint) of
solution.
* Provides reasonably safe etchant when combined with warm
water
* Supplied in 250g bags"
This is a 250g pack sufficiant to make
500ml of solution. Disolve 250g of crystals in 250ml of warm
water.
Weight
Water Solution
------
----- --------
250g 250ml
500ml
125g 125ml
250ml
50g 50ml 100ml
12. Chemical
Storage Requirements
---------------------------------
The Immerse Tin
Crystals will require.. One 250ml bottle for the solution. One 100ml
container for the remaining crystals.
The Copper Etchant will
require.. One 250ml bottle for the solution. One 250ml container for
the remaining crystals.
The Developer will require.. One 250ml
bottle for the solution. The remainer of crystals to be stored in original
packaging.
An accurate measuring jug is now required.
13.
Processing Tray Areas cm'3
------------------------------
My issue with so
many of the processing trays is that they're just so big. If you're
working with a small 3 x 4" PCB then alot of the solution will be wasted.
This examines how much solution is required for a particular area of tray.
Most liquids are metric based 1ml = 1g. A litre of liquid will generally
weigh 1Kg and displace an area of 1000cm'2. A processing tray is 25 x 30 x
5cm.
Width Length CM'2
Depth CM'3
ml
-----
----- ------ -----
------
-----
10cm
10cm 100cm'2 3cm
300cm'3
300ml
8cm 11cm 88cm'2
2cm 176cm'3
176ml
8cm 11cm 88cm'2
3cm 264cm'3
264ml
25cm
30cm 750cm'2 5cm 3750cm'3
3.75l
The largest board we can work with (due to software limitations) is
3 x 4' (7.62 x 10.16cm). Ideally a processing tray would have a flat
interior base.