Build your own UV exposure box with fluorescent like lamps

Build your own UV exposure box with fluorescent like lamps 

Ever wondered having your own UV exposure box in your lab but couldn't get one because of the high cost? Don't kill your dreams so easy. Now you can make your own UV exposure box and print your own printed circuits boards in your home. In this article we will find out how to construct the appropriate box and the required electronics inside it. This is a basic guide and not a super detailed guide. Many easy to understand thinks are missing. Don't loose more time, let's start with the specifications.

Photo from the prototype 

Dimensions Volume

Height : 33,7 cmWidth : 49 cmDepth : 27cmMax pcb dimensions: 45 x 26,5 cm

Total: 44,5 LtEffective : 28,8 Lt

Lamps Timer

Number of lamps: 4Type: BL15T8, F15BLB-T8 or BLB15T8Philips G15T8Wattage: 14,7WLamp Current: 0,3 ± 0,03 ALamp Voltage: 56VTube Length: 436 ± 1,3 mmTube Diameter: 25,5 ± 1,2 mmBase: G13Spectral Peak: 253,7 nm (UCV)UV output: 4,8WUV microwatts: 49 uW/cm² (at 1m)Average life: 8000 hrsBallast: F15T8, G15T8Glow Starter: FG1P (JIS)

  Minutes 0-99, seconds 0-5915 settable start countsLed Display to set and see the remaining exposure timeControlled with 3 push buttons

Average exposure time: 2-3 minAverage Cost: 100 Euro

ATTENTION! Do not use UVC lamps which emit hazardous radiation and is no good for exposing PCBs. Use UVA lamps which emit safe wavelengths and are good

for exposing PCBs. The tubes should either look like normal tubes or be dark blue/violet when unlit (not transparent).

1. Box Construction - Parts

In this section you will find illustrated instructions on how to build the wooden box. We used laminated wood of 1,6 mm for the frame  of the box and hardboard of 2-3mm for the back, the front panels and the small front door. First of all you have to cut the pieces in the appropriate dimensions. The best tool for that job is a fretshow. Each part's dimension that you will need is shown in the next image. 

When you finish with the cut of the above pieces it's time to find the parts you see below:

You will need 26 fasteners for wood 3cm tall, 18 wood fasteners for wood 1,5cm tall and 24 general purpose fasteners with 24 nuts. Also you will need two hinges and one grasp for you door. You can use any other material you imagine. Let your imagination work.All the inside sides must be painted white to reflect some light back.

2. Box construction – Steps

Take parts 1 and 2 and screw them together with the 3cm fasteners as the image shows.

Take part 3 and screw it with the 3cm fasteners as the image shows.

Take part 3 and screw it with the 3cm fasteners as the image shows.

Take part 5 insert it inside the frame you have created and screw it with the 3cm fasteners as the image shows 5,5cm from the bottom so part 8 which we will use later fits ok

Take part 6 and put it at the back of the frame and screw it with the 1,5cm fasteners

Take the 4 wood or metallic bars and screw them as the image shows. The three of them adjoin with the frame and one is 7,5 cm from the top.

Take parts 7 and 8 and fit them to the positions you see. Then screw them with fasteners and nuts through the bar holes.

Take part 9 and screw the two hinges on it. Then screw the hinges to the upper bar so the door can freely open and close.

You can add two small magnets to the door and two metal pieces to the frame so the door closes strongly.

Note: You must not use glue to the pieces above because after you fit them all together and have your box ready you will need to disassemble some parts in order to make the electrical connections. When you are sure your box is ready and all parts fits ok then you can proceed to the next page.

3. Lamps – Parts

First of all let's see the parts required in this section.

8 bases for the lamps with holes so they can be screwed on the wood.

2 ballasts of 40W. Each one will handle 2 lamps. This is like the common ballasts that we use on fluorescent lamps.

4 Starters (S2) capable for 15W lamps. This is also like the common ballasts that we use on fluorescent lamps.

some electronics wire for the connections

4 plastic wire canals

Some connectors

4. Lamps Install

Take of the roof of the box and screw the 8 bases of the lamps. Use the lamp to find the correct distance between them. 

Next you can add a mirror on top of roof for best reflection of light. You can attach it with some strong glue. 

Take the two plastic wire canals and put it as image shows below the roof wood. Then pass the wires from all the lamp bases thought the canals and drive them to the back side. 

Now add two canals to the two back corners of the box as the red arrow indicates. Place the roof in it's place and pass the wires thought the last added canals so they rich the bottom compartment. 

5. Lamp Connections

Follow the diagram below to wire the lamps. All connections will be done at the lower compartment of the box. Keep the 220V leads free for further connection to the timer. When 220V applied to the circuit all lamps should be on. Keep in mind that the light that these lamps emit is dangerous. Take all precautions when testing.

In the next pages we will indicate the above circuit with this: 

6. Timer Circuit

For the timer circuit we used Stan Ocker's circuit. The circuit diagram is shown below. It uses a PIC16F84 to count and display the time. The source code and the hex file are available for download. You can also download this zip that contains all the files about the timer and an info file. To program the PIC16F84 you will need a programmer circuit like this

To power the above circuit you can use this power supply for 5V setup using LM7805.

We tested the above circuit in a raster and worked nice.

You notice that the piezo speaker is replaced by a led in raster. When the countdown timer reaches zero then the led is lit. We must convert this so a relay activation will close the lamp circuit. This can be achieved with few more parts. First remove the piezo buzzer.

And attach the following circuit as the image shows:

This circuit will trigger the relay when the countdown time reach zero and then the Light Circuit is disconnected from main voltage and then lights are off.

Build the circuits on a test board and get ready to install inside the box. The led displays must be soldered on a separate test board so they can be attached in front panel of the box.

7. Timer Install

Install the led display board and the timer push buttons as the image shows. Also install a main power switch.

The general connection diagram is the following:

8. Finish

Put all together, insert the lamps and test your box. If everything is ok, then you are ready start exposing your own printed circuit boards.

9. Photos

In this page we present you some photos from the prototype. These photos can help you better understand the structure of the box. You may notice some differences but there are not critical. You can click on almost all photos for best resolution.

Cetak layout ke papan PCB

Untuk mencetak layout ke papan PCB ada beberapa cara :

1. UV Photoresist laminate

Cetak lay out ke transparant plastik film dengan laser printer.Area yang gelap akan menjadi area tembaga, dan yang transparant akan hilang / kosong. Dengan cara ini bagian yang gelap tidak akan ada cahaya UV yang bisa tembus.Dalam pemasangan negative film ini harus benar benar akurat, karena bila goyang sedikit, hasilnya akan kabur.

Persiapkan Lampu UV, dan panaskan dulu kurang lebih 2 menit sebelum memulai exposure / pencahayaan.Siapkan papan PCB yang bersih dan buat lapisan postive resist dengan menyemprotkan positiv 20.

Optional positiv resist :

1. Ada PCB yang terbuat dari bahan spesial, yang sudah ada lapisan photo-positive pada tembaga nya, bila anda menggunakan pcb ini anda tidak perlu menggunakan positive resist lagi.

2. Ada transparant film yang sudah mengandung positive photoresist, anda bisa melihatnya di site ini.

Sekarang letakkan pcb di antara 2 kaca di bawah lampu UV.Anda harus ber eksperimen dengan waktu yang di butuhkan , biasanya 3-4 menit menghasilkan hasil yang bagus. Jika terlalu lama di sinari, maka akan lebih banyak area yang hitam, sehingga hasilnya kurang sempurna . Setelah 3-4 menit, matikan lampu UV dan ambil PCB, biarkan sampai dingin, karena suhu nya sangat panas (30-40 derajat celcius), dan jika di taruh langsung ke cairan developer, maka reaksi nya akan terlalu cepat, sehingga anda akan kehilangan sebagian gambar layout.

Setelah dingin, masukkan ke cairan developer.

Ketika anda membeli bubuk atau cairan NaOH, anda bisa melihat labelnya untuk cara penggunaan nya, harus di campur dengan air dengan perbandingan berapa banding berapa.proses developer ini membutuhkan waktu kurang lebih 1-2 menit, lalu ambil PCB dan siram dengan air untuk menghilangkan sisa larutan NaOH.

Optional developer :

1. DP50 developer, 50 gram sachet di campur dengan 1 liter air, dapar menghasilkan cairan developer minimum 10 x 100x150mm PCB.

2. Bahan dasar Silicate , berbentuk cairan concentrate. Namanya sodium Metasilicate pentahydrate Na2SiO3*5H2O

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