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Old 19th February 2013, 07:38 PM   #11
xrk971 is offline xrk971  United States
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Is it crazy? I was going to skip the breakout board - so no PCB whatsoever - just gluing everything to a board to stabilize before point-to-point soldering. The upside chip actually provides good access to the pins for soldering each one with a fine wire like how dies are attached inside an IC. I have a printed PCB on the way, but wanted to try this crazy idea of a dead bug TPA amp.
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Old 19th February 2013, 07:57 PM   #12
rsavas is offline rsavas  Canada
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"Is it crazy?" I do not think that you will get anyone to disagree, but hey to each there own, as the saying goes.
Let us all know how your manual wire bonding excercise goes :-)
Steady as she goes.
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Old 19th February 2013, 08:08 PM   #13
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Quote:
Originally Posted by rsavas View Post
And you want to do what?, try to solder onto the leads hanging in the air = crazy!!
Drill a hole through the center of the exposed pad on the PCB, enough to get the soldering iron tip to heat up the exposed pad, on the IC & the PCB, next, solder the components leads as usual, right side up, then finally solder the exposed thermal pad afterwards.
This is what I do if possible, drill a 2-3mm dia hole where the pad should be, affix the chip as normal, flip the board then solder the exposed pad. To do this I flow in a lot of solder till the whole is filled to the reverse copper plane with a plug of solder. It works fine and even with LEDs if you're very careful to limit exposure time with a low temp iron.

If a part is too small I drill a 1.5mm hole and place a 1.5mm copper rod through the hole, sanded flat beneath the chip and soldered to the backside copper with tin solder. I then solder the rest of the chip in place with lead based solder paste + cheapo small electric oven/hot air gun (the oven works better).


The tpa is big enough for the first method to work well.
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Old 19th February 2013, 08:38 PM   #14
xrk971 is offline xrk971  United States
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5th Element,
I thought of doing the very thing you describe. When I get a PCB I will use the TPA3116 which has the thermal pad on top for a heatsink. For grins, I am going to do the dead bug manual wire bonding approach with the SMD components glued to a foam core board with PVA glue. I think the biggest thing I have to watch for is bridging the pins. They are spaced 0.6 mm - pretty small but we will see... Slow and steady, I think the magnifying googles will help. I fear it will not work but the chips are cheap to try and I will have a "foam core amp" to go with my foam core speakers!
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Old 19th February 2013, 08:51 PM   #15
rsavas is offline rsavas  Canada
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Actually 0.5mm pitch, good luck Mr Foam Core!!
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Old 24th February 2013, 01:28 PM   #16
xrk971 is offline xrk971  United States
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Default Foam Core Amplifier begins

Ok, so I took all your suggestions and agree that this is crazy but I am doing it anyway. I laid out the smd components and glued them in place with acrylic clearcoat (smd) and hot melt for larger thru hole stuff and terminals. There is a layer of foil underneath paper for ground plane. The whole thing is on a 4 x 6 inch foam core board. Note the dead bug upside down TPA3118 chip. This was actually pretty fun to do. The hard part of soldering is next. Slow and easy...
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Old 26th February 2013, 03:28 AM   #17
xrk971 is offline xrk971  United States
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My magnifying goggles came today - wow what a difference they make. I can actually see the text on the resistors (0603 size) which are the size of a flea. The binocular goggles have a 3x flip down lens on top of the 1.5 x main lens and a 9x swing out loupe all with LED illumination. Very handy. As soon as I have some time I will start the manual wire bonding with a soldering iron and flux core solder. I am told liquid flux in a hypo syringe is key for this sort of stuff but that would results another order.
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Old 26th February 2013, 09:46 AM   #18
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It will be easier to solder the chip on the adaptor then solder the rest of the part around it. Soldering wires directly on those 0.5mm pitch pins is not gonna be easy, even if you have the proper PCB for it without the right tools and experiences/skills can be a challenge.

Why not make PCB for it? its a useful skill to learn than doing it that way LOL.

Well good luck, let us know how it goes.
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Old 26th February 2013, 10:14 AM   #19
xrk971 is offline xrk971  United States
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I may have to go with an adapter the next time if this fails. I think the hardest part will be soldering wires to the pins, which are actually 0.6 mm pitch according to drawings. I plan to use thin wire wrap style wires for connections to pins. Making a pcb will definitely be something I want to do at some point if the bug bites me, kind of like making speakers. I don't want to do the actual acid etch and screen printing, drilling myself. Using a pcb fab house is only option and they are charging $70 per run of 3 boards. Do you guys have suggestions for a fabricator? They all have software you can download and start designing boards with. I am worried about making a mistake and you are stuck with bad boards.
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Old 26th February 2013, 10:26 AM   #20
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Hey X,

Show us a photo of those glasses! And if possible a link to where you got them on Amazon.

There's bunches of them out there, and I'd like to get a pair that's worth the money.

Happy soldering!

I was just looking at that "breakout board" you mentioned earlier. That's interesting and probably worth the $10.

Mark
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