Making a PCB using Ultra Violet Photo Resist

[@cravenmoorehead7099]

Jesus….you work like a child

[@DevelopIT]

Great comment, you'll probably like some of my other videos.

[@margaretslater1354]

I use a laminator works beautifully. Put between clean white paper

[@abhisekroy7426]

Is it necessary to use laminator or the heaters? What if I skip that part? And directly put a mask on it and expose to UV?

[@Berghiker]

That exposure box is perfect! I'm going to make one just like it. Thanks.

[@Berghiker]

What is the value of the resistor you are using with the 24 UV LEDS and the LED indicator ? I am using 6V minus the 2V drop across the indicator LED leaves me with 4V. With a 22 ohm resistor, I calculated a current of 272mA for the 25 LEDs. 11mA each.

[@Berghiker]

Is Sodium Hydroxide better to use than Sodium Carbonate for the developer? I tried with NaCO3 and did not get great results. I need to rub the board gently with my finger afterwards.

[@philt8322]

Hi Thank you for a very informative video. I will give this method a try.

[@DevelopIT]

Thank you. Of the two methods I have tried, I prefer the heat transfer paper one, as it is simpler and quicker. I was thinking in future I may try the UV Photo resist to apply solder resist to a PCB at home, and maybe a silkscreen layer.

[@Berghiker]

@@DevelopIT It's simpler and quicker but worst quality and not very consistent results.

[@JavierChiappa]

Love all those little boxes, lol

[@Berghiker]

How do I get more current to flow through the leds? The voltage is 3.5V but it is not bright enough. All the 24 LEDS are connected in parallel. No resistor on the emmitter or collector of the BD139. 1K goes to the base. I'm using a standard 555 timer with 4V.

[@DevelopIT]

You can adjust the resistor value on the base of the transistor or increase the voltage to the circuit (keeping within the voltage specification of all of the components).

[@Berghiker]

@@DevelopIT I am using the boost buck converter, so it will need to stay at 4VDC.

[@Berghiker]

If you run the UV leds directly off 4v then you have no current limiting resistor in series with each LED? Is that right?

[@DevelopIT]

The resistor into the base of the transistor will also limit current. The transistor has a gain (hfe), what ever current passing into the base will be amplified by the gain of the transistor.

[@Berghiker]

What's the max current rating on the output for that boost converter?

[@Berghiker]

Is your 555 IC working on 4VDC from the output of the converter or are you using a CMOS one?

[@DevelopIT]

I'm probably using a CMOS version.

[@Berghiker]

I made the same exposure box and circuitry like you did. Is the exposure time of 30 seconds enough?

[@DevelopIT]

Experiment to find the best settings for your LEDs and film specifications.

[@murraymadness4674]

nice video, thanks for showing how you do this. I don't have the patience to wait 2 weeks for delivery of the $2 boards from china, but they are probably why I don't see many doing this anymore. but i have a bunch of bare coppy boards and a big roll of uv photoresist so gonna do it this way. After failing for 2 weeks I will then get the chinese boards in the mail, so no worries. :)

[@DevelopIT]

I'm the same, I use the heat transfer paper method as I find it easier. Though most of the PCBs I want currently are a bit too complex to make at home easily.

[@djpenton779]

Useful to me. Thanks.

[@Berghiker]

I am using 500mA with 24 UV LEDs. Are you using the same power for 30 seconds?

[@DevelopIT]

Try experimenting, expose for longer time, see what works for you.

[@Berghiker]

Is that a BD139 NPN driving the output?

[@DevelopIT]

It is, but it's only switching the output so any bi-polar that is capable of driving the current you require.

[@Berghiker]

Is it better to use Sodium Carbonate developer or Sodium Hydroxide developer?

[@DevelopIT]

I have never used Sodium Hydroxide, let me know how it goes.

[@Berghiker]

I made this UV exposure box that you made and it did not expose the board. Maybe I should use a heater gun like you used instead of the laminator. The exposure time was exactly 30 seconds. So right now I am very disapointed!! to say the least.

[@DevelopIT]

I have never used a laminator for this, so don't know what issues you are having.

[@Berghiker]

Can I see the 555 timer circuit that you used?

[@DevelopIT]

I didn't draw a circuit for this project, I just used the mono-stable circuit in the datasheet for the 555 timer.

[@Berghiker]

Is that photo resist film from Banggood?

[@DevelopIT]

I got it from eBay, a seller from China.

[@Berghiker]

How much current is each LED getting?

[@DevelopIT]

I didn't measure. The LEDs I got seemed to run fine at 4V, but I have no idea of the spec of the LEDs, I'm probably over powering them. LEDs can vary significantly in specification.

[@Berghiker]

Can you give me the link to that inverter you bought?

[@DevelopIT]

I would have got it from eBay. It was a while ago, I would have searched for something like "buck boost converter" and ordered by price ascending.

[@Berghiker]

@@DevelopIT Ok. I found it. Thanks.

[@jhonnyambarita236]

thanks

[@Amirt1999]

Thank you :)

[@Berghiker]

With your exposure box, I found that 8 mins exposure time is perfect and 2 mins in the NaCO3. I don't understand that only 30 seconds is enough for you. Beats me. It's not making any sense.

[@DevelopIT]

I'm probably putting too much current though the UV LEDs. Though there are a number of possible reasons. There are two frequencies the UV LEDs are available in, we may be using different ones. My UV film may be more sensitive. I only made a few boards this way, I found I prefer the heat transfer process of apply and ferric chloride; more preferable to UV apply, expose, develop, rinse and ferric chloride.

[@Buciasda33]

Thanks, but use gloves 🧤 and just rub with your fingers in the sodium carbonate. Then use a paint brush, not the toothbrush. Actually you can use the toothbrush to scrape off the Crured Film at the end. And now I see where I fucked up the process: 1. I didn't remove the top film before applying the UV Mask and the film probably moved around a bit and the UV Light dispersed through the film leaving me with a mess... 2. I used H2SO4 to clean up the Cured Photoresist Film, which only takes 2 seconds, but also started dissolving my traces... If I remember correctly...

[@DevelopIT]

Good point about the toothbrush, it is a bit aggressive for the job. I tried the UV method to see how easy it was. I now use the heat transfer method as I find it much simpler.

[@Buciasda33]

@@DevelopIT it's simpler, but you have to get the pressure, time and temperature right and you don't always get a good transfer

[@Berghiker]

Why is the board not very clear to see if it has been exposed properly? You can hardly see if it has been exposed.

[@DevelopIT]

When I exposed boards the exposed areas where clearly darker colour. Make sure to keep the photosensitive film away from light in case it has been accidentally exposed prior to use.

[@firmman4505]

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