Preparing the UV Chamber and Board - Revision history

Aplstudent: /* Exposure in the UV Chamber */

2019-04-11T20:27:59Z

‎Exposure in the UV Chamber

Aplstudent: /* Exposure in the UV Chamber */

2019-04-11T20:27:46Z

‎Exposure in the UV Chamber

Aplstudent: /* Exposure in the UV Chamber */

2019-04-11T20:24:04Z

‎Exposure in the UV Chamber

Aplstudent: /* Double Side Board */

2019-03-09T21:04:30Z

‎Double Side Board

Aplstudent at 20:52, 9 March 2019

2019-03-09T20:52:13Z

Aplstudent: /* Exposure in the UV Chamber */

2019-02-28T19:56:16Z

‎Exposure in the UV Chamber

Aplstudent: /* Double Side Board */

2019-02-28T19:53:52Z

‎Double Side Board

Aplstudent: /* An Alternative Approach: */

2019-02-28T19:52:16Z

‎An Alternative Approach:

Aplstudent: /* Exposure in the UV Chamber */

2019-02-19T21:23:42Z

‎Exposure in the UV Chamber

Aplstudent at 21:23, 19 February 2019

2019-02-19T21:23:22Z

@@ Line 45: / Line 45: @@
 ==Exposure in the UV Chamber==
-Before you begin exposing your board, read the next section ([Developing the Board]) and make sure that you have a prepared tray of mixed NaOH and water nearby. The NaOH solution removes photoresist and you risk unintentional overexposure from over-head lighting if you leave your exposed board out while preparing the NaOH solution. To avoid UV exposure from the florescent lights preform the UV exposure step in the quantum optics room with only the green overhead lights.
+Before you begin exposing your board, read the next section ([[Developing the Board]]) and make sure that you have a prepared tray of mixed NaOH and water nearby. The NaOH solution removes photoresist and you risk unintentional overexposure from over-head lighting if you leave your exposed board out while preparing the NaOH solution. To avoid UV exposure from the florescent lights preform the UV exposure step in the quantum optics room with only the green overhead lights.
 With the board assembly on the middle glass plate, put the upper diffuser plate in place if appropriate, close the lid, and turn the chamber on. The eerie violet glow should immediately appear.

@@ Line 45: / Line 45: @@
 ==Exposure in the UV Chamber==
-Before you begin exposing your board, read the next section ([]) and make sure that you have a prepared tray of mixed NaOH and water nearby. The NaOH solution removes photoresist and you risk unintentional overexposure from over-head lighting if you leave your exposed board out while preparing the NaOH solution. Preforming the exposure step in the quantum optics room with only the green overhead lights on protects your board from the stray UV light of the florescent overhead lights.
+Before you begin exposing your board, read the next section ([Developing the Board]) and make sure that you have a prepared tray of mixed NaOH and water nearby. The NaOH solution removes photoresist and you risk unintentional overexposure from over-head lighting if you leave your exposed board out while preparing the NaOH solution. To avoid UV exposure from the florescent lights preform the UV exposure step in the quantum optics room with only the green overhead lights.
 With the board assembly on the middle glass plate, put the upper diffuser plate in place if appropriate, close the lid, and turn the chamber on. The eerie violet glow should immediately appear.

← Older revision		Revision as of 20:24, 11 April 2019
Line 44:		Line 44:

	==Exposure in the UV Chamber==		==Exposure in the UV Chamber==
		+
		+	Before you begin exposing your board, read the next section ([]) and make sure that you have a prepared tray of mixed NaOH and water nearby. The NaOH solution removes photoresist and you risk unintentional overexposure from over-head lighting if you leave your exposed board out while preparing the NaOH solution. Preforming the exposure step in the quantum optics room with only the green overhead lights on protects your board from the stray UV light of the florescent overhead lights.

	With the board assembly on the middle glass plate, put the upper diffuser plate in place if appropriate, close the lid, and turn the chamber on. The eerie violet glow should immediately appear.		With the board assembly on the middle glass plate, put the upper diffuser plate in place if appropriate, close the lid, and turn the chamber on. The eerie violet glow should immediately appear.

← Older revision		Revision as of 21:04, 9 March 2019
Line 18:		Line 18:

	Now, remove the tape from the film and use the L shaped jig in the UV curing chamber to line up your bottom layer artwork, the PCB, and your top layer artwork. Lastly, place a sheet of glass on top of the artwork/PCB/artwork layer. The glass will keep all the different components lying flatly against each other.		Now, remove the tape from the film and use the L shaped jig in the UV curing chamber to line up your bottom layer artwork, the PCB, and your top layer artwork. Lastly, place a sheet of glass on top of the artwork/PCB/artwork layer. The glass will keep all the different components lying flatly against each other.
		+
		+	It can be very difficult to lay the PCB on top of the bottom piece of lithographic film without moving the film, and also difficult to lay the top sheet of glass on top of the top piece of lithographic film without moving it. If you are having trouble with alignment you can see the alternative approach below or drill a few holes in the PCB to help you align the through holes or vias on the lithographic film.

	===An Alternative Alignment Approach:===		===An Alternative Alignment Approach:===

← Older revision		Revision as of 20:52, 9 March 2019
Line 1:		Line 1:
−	Before getting any boards out, the UV chamber must be prepared. Get a VIS optical power meter out and lay the detector face down on the middle glass plate. Set the wavelength to 400nm (the actual wavelength is centered on 365; This introduces a roughly 40-50% shortage in measured power, if one is interested in absolute terms).	+	Before getting any boards out, the UV chamber must be prepared. Get a VIS optical power meter (this detects light in the visible wavelength spectrum) out and lay the detector face down on the middle glass plate. Set the wavelength to 400nm (the actual wavelength is centered on 365; This introduces a roughly 40-50% shortage in measured power, if one is interested in absolute terms).

	Plug the lid power connections in, turn the power level all the way off, close the lid and zero the OPM, and turn the chamber on. Dial the potentiometer until the power level reads about 200uW. Kill the power, remove the lid and put the OPM away.		Plug the lid power connections in, turn the power level all the way off, close the lid and zero the OPM, and turn the chamber on. Dial the potentiometer until the power level reads about 200uW. Kill the power, remove the lid and put the OPM away.

@@ Line 43: / Line 43: @@
 ==Exposure in the UV Chamber==
-With the board assembly on the middle glass plate, put the upper diffuser plate in place if appropriate, close the lid, and turn the chamber on. The eeiry violet glow should immediately appear.
+With the board assembly on the middle glass plate, put the upper diffuser plate in place if appropriate, close the lid, and turn the chamber on. The eerie violet glow should immediately appear.
-Minimum exposure time, with an OPM reading of 200uW, is roughly 1m30s. Because the lithographic film has an enormous contrast ratio, there is a substantial margin for overexposure.
+Minimum exposure time, with an Optical Power Meter (OPM) reading of 200uW, is roughly 1m30s. Because the lithographic film has an enormous contrast ratio, there is a substantial margin for overexposure.
 The margin is NOT a thousand times one minute: Edge effects (light diffracting around borders, and arriving at an angle, etc) mean that excessive overexposure will cause sufficient exposure to strip the mask to gradually bleed outwards from intentionally-exposed areas.
 Inadvertently, a board was exposed for 7 minutes; This was sufficient to cause isolated thin copper rings to shrink very appreciably.

@@ Line 17: / Line 17: @@
 [[File:Artwork Alignment Cuts.png]]
-Now, use the L shaped jig in the UV curing chamber to line up your bottom layer artwork, the PCB, and your top layer artwork. Lastly, place a sheet of glass on top of the artwork/PCB/artwork layer. The glass will keep all the different components lying flatly against each other.
+Now, remove the tape from the film and use the L shaped jig in the UV curing chamber to line up your bottom layer artwork, the PCB, and your top layer artwork. Lastly, place a sheet of glass on top of the artwork/PCB/artwork layer. The glass will keep all the different components lying flatly against each other.
 ===An Alternative Alignment Approach:===

@@ Line 19: / Line 19: @@
 Now, use the L shaped jig in the UV curing chamber to line up your bottom layer artwork, the PCB, and your top layer artwork. Lastly, place a sheet of glass on top of the artwork/PCB/artwork layer. The glass will keep all the different components lying flatly against each other.
-===An Alternative Approach:===
+===An Alternative Alignment Approach:===
 Making a double sided board introduces a new technical hurdle: The requirement that the near and far sides be aligned within a few thousands of an inch, with a completely opaque and finitely thick layer between them!

@@ Line 41: / Line 41: @@
 Once the film, plate and board are positioned, lay the upper thin glass plate down. Use some small aluminum blocks to provide a small amount of weigh-down; Upon very close inspection, it should be clear that there is no (or next to no) air gap between the emulsion and photoresist via lack of any shadow.
-===Exposure in the UV Chamber===
+==Exposure in the UV Chamber==
 With the board assembly on the middle glass plate, put the upper diffuser plate in place if appropriate, close the lid, and turn the chamber on. The eeiry violet glow should immediately appear.