the back of the board

[mbeals 74]

I've been thinking the last few days about two ideas.  One is to etch symbols or text into a copper pour, then mount LED's upside down on the backside such that they illuminate through the board.  The other one is to make a cutout in the board with pads on the backside, but not mirrored, so I can mount an IC upside down in the hole, letting it sit much flatter than traditional surface mount.

 

I know these ideas can't be original to me, but google has not turned up any examples of either.  Has anyone here tried either of these things?  How did it wind up working out?

[roadrunner84 466]

The first one (LEDs upside down) are known as "flip chip". The other one I don't know about the name, I see that setup in particular with transformers (eg: in display inverter boards)

 

Never mind, flipchip is about the wirebonding technique, not about the whole LED being upside down.

[juani_c 66]

The other one is to make a cutout in the board with pads on the backside, but not mirrored, so I can mount an IC upside down in the hole, letting it sit much flatter than traditional surface mount

something like this perhaps;

http://www.t4f.org/projects/business-card

[Lgbeno 189]

There are reverse mount LEDs that shine through a hole in the pcb. The application is if you have a cap touch bottom or something like that and you wanted to light it up but it still needed to be flat.

 

http://www.avagotech.com/pages/en/leds/surface_mount_chipleds/reverse_mount_series/

 

I think the chip in the hole idea is kinda cool, you should ge for it. I know that you would never be able to have a automated pick and place machine do the asm unless the parts were flipped and then re taped or put onto a tray but for hand assembly, pretty cool.

[roadrunner84 466]

that buiness card is the shit! I mean it is:

• business card
• oscilloscope
• logic analyzer
• I/O board
• serial to usb
• mass storage
• portfolio

all in one!!

[Fred 453]

I was thinking of doing something similar for a while but disappointed that I've been beaten to it before I got round to it. Most "business card" PCBs are so hugely thick and clunky and miss the point. If you're going to go for that sort of form factor then go for it and do it properly - like the T4F one.

 

I CNC mill my boards so a well aligned cutout for a cap sensing G2452 shouldn't be too much of a problem. I also think that you could probably mount a CR2012 battery pretty much inside the PCB too, but you need to make a custom battery holder..

[cubeberg 540]

I remember seeing something (I think it was on hackaday) - similar to that business card, but for several parts.  I'm pretty sure there was a QFN chip that was upside-down.  Unfortunately - I can't no matter how I search.  There was also one PCB business card where they used a very thin PCB, and another on top with cut-outs for the parts - http://hackaday.com/2012/10/04/limpkins-new-business-card/.  Certainly ups the manufacturing cost though.

[mbeals 74]

That's exactly what I was looking for.  That stacked board looks quite interesting...too bad you would need to order a ton of them to make it feasible cost-wise.  I suppose if I deviated from standard size and used a 5x10cm card, I could just panelize the top and bottom halves.

 

I did look at those reverse mounted LED's, but I was hoping to do it without a hole.  I was going to try to etch a negative image in the copper so that the LED on the back would illuminate the symbol like a front panel display.

[TheDirty 33]

The Energy Micro devel watch does this.  They have a QFP, crystal, caps, and the LCD connector mounted in holes in the board.

 

Half way down.

http://blog.energymicro.com/2012/12/12/make-a-slim-watch-with-arm-cortex-m3-efm32/

[cubeberg 540]

The Energy Micro devel watch does this.  They have a QFP, crystal, and caps mounted in holes in the board.

 

Half way down.

http://blog.energymicro.com/2012/12/12/make-a-slim-watch-with-arm-cortex-m3-efm32/

That's the link I was looking for!  Here's the HaD post - http://hackaday.com/2012/12/12/super-slim-wristwatch-build/

Thanks for finding that TheDirty!

[mbeals 74]

that battery mount is intriguing.  I've been trying to figure out how to pull that off since most SMD mounts use the board itself as the backside of the holder.  I considered using a vertical mount coin cell holder on its side in a cutout   

 

 

Is there a way in EAGLE to place a component on the bottom layer without mirroring it, or do I need to make a custom package?

[cubeberg 540]

I don't think so.  However - you could copy the package, mirror it, and then switch to top layers.

You'd need to create the cut-out anyway - probably easiest to do a custom package.

[mbeals 74]

Can the cutout be placed in the package?  I figured I would need to add it manually to the board itself.

[cubeberg 540]

Absolutely - just use the same layer as you do when you create your board outline.  Someone created a generic boosterpack part that already had the board outline for the standard 5cm x 5cm size.  I just positioned it and added my components within that.  You should be able to do the same with your part.