Aoyue Quad Flat Pack Nozzle

[Trash80toHP_Mini]

and[/i] soldering a replacement CPU?

 

[uniserver]

i just use my heat gun to change cpu's

my hot air reflow doesn't seem to have enough gusto.

 

[techknight]

Because you need lower heat preheating..

Use a pancake griddle. You rework wand will work then and youll have no boardwarp

 

[Trash80toHP_Mini]

Cool, another Goodwill goodie to snag!

Back to the main question, is this the right too for off and back on? :?:

 

[uniserver]

sure that is what apple used in their re-work dept.

 

[Trash80toHP_Mini]

My computer is flash-proofed, but I believe you. [)] ]'>

 

[uniserver]

lol its funny they were removing and reinstalling a VLSI I/C for a 5120 mac portable board.

 

[bigmessowires]

How do you solder a 100-pin chip with a heat gun? I've only ever used mine for de-soldering.

Unless you've got a correct size stencil to apply solder paste, where does the solder come from that gets liquified by the hot air?

 

[Trash80toHP_Mini]

I found a stencil and something else(?) package deal for that proc at some point in the last 5 years, so that's on the list as well. I'm not bothering with anything but the griddle before I noodle out the traces for the bus multiplier/clock rate resistors Apple hid somewhere on the 2300c . . .

. . . bat rastards!

 

[uniserver]

what i use, is the solder that is already on the pads… + Flux is the key… with flux the solder flows just like it should.

if there is a lack of solder on the pads then i will add some/ before installing the I/C.

just as i did here adding ram to this card.

viewtopic.php?f=29&t=22476

 

[bigmessowires]

Huh, maybe I'll try that sometime on a junk board. I can see how re-using the existing solder would help, but won't it be kind of uneven and lumpy, making it very hard to position the new chip so it's leveled and squared?

I once tried soldering a TQFP chip on a virgin board by tinning the pads with a soldering iron, placing the chip on top, and then hitting it with hot air. It didn't work very well, so I've used the drag-solder technique with an iron ever since. Maybe I should try it again?

 

[uniserver]

yeah i use the heat gun, the hot air re-work does not really have enough heat energy for my liking.

plus i have been using the heat gun before the hot air station over the last year, so i am use to it.. and my arm automatically regulates the heat gun temp for me

Flux… Flux is what balls up the solder an makes it flow like liquid mercury.

you can see my joins here they look nice.

[attachment=0]Screen shot 2014-01-08 at 1.45.50 PM.jpg[/attachment]

some of the other ram chip joints might look a little hairy, but that is only because was getting lazy and not applying the flux properly.

there is a trick to getting the chip on there… you hold the chip right in line of heat gun so the chip pre heats. then once the pads are liquid you set the chip ont there and if all is well it flows right into place self-centering!

kinda like with the Fill rod when tig welding.

 

[bigmessowires]

there is a trick to getting the chip on there… you hold the chip right in line of heat gun so the chip pre heats. then once the pads are liquid you set the chip ont there and if all is well it flows right into place self-centering!

OK, so you've pre-tinned the pads (or have solder already on there from the old chip). Then you hold the chip with tweezer or something? And then hold it just above the board, so the air stream is heating the chip and the pads at the same time? I think I don't have the right mental picture.

 

[uniserver]

yes! and flux too dont forget the flux

then afterwards i clean up the flux with acetone and a tooth brush.

 

[Trash80toHP_Mini]

When you're doing an unpopulated board, I've heard of laying the parts right onto the pasted pads and then surface tension centers them perfectly when the paste melts in the toaster oven.