One of more advanced PCB manufacturing methods is exposing laminate copper boards covered by photo resistive layer through mask. Using UV light in manufacturing PCBâ€™s has many benefits according to other methods: you can get thin tracks like 0.2mm. You couldnâ€™t do this by using other home techniques like laser printers or hand artwork; other advantage is that this method gives clean image â€“ smooth edges of PCB tracks. Little bit effort and you can compare results to commercial products. And pf course third benefit is speed and multiple replications of your boards by using the same mask. In this article is described the manufacturing of an automatic ultraviolet light source exposure box.
Parts for UV box
Case with organic glass
UV lamps ballasts and starters
Case is made of 5mm wood board wired with screws.
Making a control panel
Control panel consists of two parts:â€Power controlâ€ and â€œAutomatic controlâ€
POWER switch is used to turn on/off power of the UV box. Green LED indicates the ON. MANUAL/AUTOMATIC switch is used to power l the UV lamps manually or automatically. Switches UPSIDE and UNDERSIDE are used to enable upper and lower lamps separately â€“ in case you are using single or double sided boards.
When automatic mode is selected, then by pressing buttons MIN UP, MIN DOWN, SEC UP, SEC DOWN exposure time is selected. START starts timer counter and powers the lamps through relays. STOP/CLEAR is not implemented yet. LCD displays the Time of exposure, and after start is pressed it shows remaining time of UV exposure.
There are used 8 PHILIPS TL 20W/52 lamps in this exposure box on each side. Some technical characteristics:
All view of lamps installed.
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To make all the float of light towards the PCB there is Aluminum foil used. It also makes illuminations smoother.
The intensity smoothness viewed on white paper sheet at distance 5 cm from lamps.
The UV box is controlled by 8 bit microcontroller AT90s2313 from ATMEL. Circuit diagram is shown bellow:
Control circuit is very simple. Buttons are connected directly to I/O pins through internal Pull-Up resistors. When button is pressed â€“ the â€œ0â€ level in port input is generated, which triggers an action.
Buttons MIN UP, MIN DOWN, SEC UP, SEC DOWN are used to select UV exposure Time. START is for starting Exposure and count down. LCD displays time remaining.
There is standard HD44780U LCD 6×2 characters used. Lamps are controlled through 5V relays.
There you can see some Pictures of PCB.
Lamp control and power source
UV lamps are connected in series of 2 and then ballasts are connected. Starter is connected to lamps in parallel. Upper and lower covers of box can be controlled separately by using switch. In this circuit you can also see power control for microcontroller and relays.
Putting it all together
Other examples you can see in my ARM section.
Download source code: Source Code