Probably wouldn't make a difference but I was planning on using the wire to get the heat to the ball to reflow it. That would burn all the insulation off. I ordered PTFE insulated wire, so the insulation might survive.
Den onsdag den 28. oktober 2015 kl. 01.41.25 UTC+1 skrev krw:
how many balls are on the chip?
if it is the outer row you don't need insulation
-Lasse
I tried a few of our PCBs with BGAs, and I was able to slip a stripped wire-wrap wire, #30, under all the BGA chips. You could squash it flat a little if it was too tight. Seems to me, the real problem will be to make the connection.
I guess you could tin the wire, reheat the BGA, and make the solder connection. Tricky.
Push a needle into the ball?
Conductive epoxy?
We have a cool optical thing here that gets low on the board and snoops the BGA from the side. Something like that would help.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
100
Probably not. I was going to glue the resistor and cap to the top of the chip. The board is *really* dense (900 some components in about
120x150mm), so there isn't a lot of room for the parts.
Yes, there is that problem. Worse, it's RoHS crap.
I'm hoping to get enough heat through the wire.
I can see the balls with my Mantis. I can mount the board in a vice so I can view it edge-on. Again, we have an XRAY machine to check the connection. I can also check the connection by measuring the voltage and check for shorts to adjacent pins. I think we can do a good job of checking the work.
Den onsdag den 28. oktober 2015 kl. 02.10.57 UTC+1 skrev krw:
solder the wire to the ball bend it around and glue it to the top before you place it in the solder paste and reflow?
-Lasse
Wow, I think you are going to find this really tough. The wire has such small cross section, and the ball is heat sunk from both sides, mayve 20 X the cross section on EACH side. This is going to be really hard. I think you are going to have to put the soldering tip right into the ball to melt it.
Jon
That's a really good idea. I'll probably try that if we have to pull the BGA. The supplier told me they'd send another 100 samples, though some will be needed for future builds (they're changing the chip and will discontinue this one).
I don't see how a tip is going to fit under the part. But you're probably right. I'm sure I'll have to use air, too. If I go this way, I'll have to be really careful to keep from reflowing all of the balls.
Den torsdag den 29. oktober 2015 kl. 01.23.32 UTC+1 skrev krw:
if you tack down the chip with a few dots of clue so it it can't move reflowing all the balls is probably not a problem
-Lasse
It won't go anywhere anyhow. But the board should be flat.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Den torsdag den 29. oktober 2015 kl. 18.41.19 UTC+1 skrev John Larkin:
if you are trying to melt a ball and poke a wire into it while holding the board at an angle where it is possible to see what you are doing, I think there a risk you might melt all the balls and bump it ;)
-Lasse
Yup. That's why it helps to have some optics that lets you see the balls from the side, while the board lays flat.
We have a gadget that does this. When we lay out a board, we leave a little room around the parts for this guy to sneak in.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Den fredag den 30. oktober 2015 kl. 00.10.36 UTC+1 skrev John Larkin:
needs more heat ;)
-Lasse
Those pics are from our zombie horror collection.
Some (I hope most) were assembled by outside contractors.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
That'd be hard. maybe use a loop of nichrome wire and thin it in the middle like a soldering gun and feed it DC until it melts the ball even that doesn't feel paticularly practical.
Hot air reflow is probably your best bet.
-- \_(?)_
The CM said they've been playing with the boards they used to profile the oven. They made a hook at the end of a wire and were able to reflow the ball into the hook. They want some of the real boards to try next. If they're successful, I'll have them do all of them. If some fail, I can use some of the boards without USB.
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