Maker Pro
Maker Pro

SMD chips

Hi;

I could use a bit of direction here. I have a RDA9330H to change, small
44 pin IC. Now I can get this done, just don't drink too much coffee
before work. Thing is, I saw other chips on the board with only ½ the
space between the pins and I am wondering how they are changed.

I have heard of heat guns, we have a magniying glass, but I need more
of the nuts and bolts of the process. I have changed a few LSI chips,
but the technique was less then optimal.

I cut the leads off the chip with a razor. Broke it off the glue, and
then painstakingly removed the bits so the new chip would seat
properly.

After tacking the new IC at opposite corners I flooded the sides with
solder, then wicked off the excess. This actually worked a bunch of
times on like the 44 pin QFP (I think) package of the TDA9330H. I
remember doing a bunch of them in Hitachi built camcorders. The digital
servo IC lost the phase lock for the capstan, and handled by the freq
lock alone caused massive wow and flutter. I had three or four of them,
after they were in top notch mechanical condition, they still had the
wow and flutter. It had two different pins for the phase and freq lock,
and they were not integrated exactly the same into the capstan control
voltage.

I did those differently, I used a guitar string for removal. I am not
worried about changing this 44 pin QFP. I am worried about the other
ICs on the board. Some of them pins got a mighty fine pitch. What do
you all do ? is it a hot air gun, or are we destined to become board
jockeys ?

Just figuring things out, a heat gun would soften the glue. Enough heat
would melt the solder and you just lift it off. Then, getting the new
IC aligned wqith some sort of jig, with downward pressure you should be
able to make it flow.

Even if this becomes feasible, we are not talking BGA ICs here. On
those I simply don't know.

Thanks in advance.

JURB
 
A

Arfa Daily

Jan 1, 1970
0
Hi;

I could use a bit of direction here. I have a RDA9330H to change, small
44 pin IC. Now I can get this done, just don't drink too much coffee
before work. Thing is, I saw other chips on the board with only ½ the
space between the pins and I am wondering how they are changed.

I have heard of heat guns, we have a magniying glass, but I need more
of the nuts and bolts of the process. I have changed a few LSI chips,
but the technique was less then optimal.

I cut the leads off the chip with a razor. Broke it off the glue, and
then painstakingly removed the bits so the new chip would seat
properly.

After tacking the new IC at opposite corners I flooded the sides with
solder, then wicked off the excess. This actually worked a bunch of
times on like the 44 pin QFP (I think) package of the TDA9330H. I
remember doing a bunch of them in Hitachi built camcorders. The digital
servo IC lost the phase lock for the capstan, and handled by the freq
lock alone caused massive wow and flutter. I had three or four of them,
after they were in top notch mechanical condition, they still had the
wow and flutter. It had two different pins for the phase and freq lock,
and they were not integrated exactly the same into the capstan control
voltage.

I did those differently, I used a guitar string for removal. I am not
worried about changing this 44 pin QFP. I am worried about the other
ICs on the board. Some of them pins got a mighty fine pitch. What do
you all do ? is it a hot air gun, or are we destined to become board
jockeys ?

Just figuring things out, a heat gun would soften the glue. Enough heat
would melt the solder and you just lift it off. Then, getting the new
IC aligned wqith some sort of jig, with downward pressure you should be
able to make it flow.

Even if this becomes feasible, we are not talking BGA ICs here. On
those I simply don't know.

Thanks in advance.

JURB

Friend of mine had the gear to do ICs like those that you mention. It was a
proper infra red rework station that heated the board from below, as well as
training hot air I think on the top, so it was able to handle BGAs as well.
The chip was removed and repositioned by automatic vacuum pen, the board
being clamped in the base of the station. Everything was monitored by a
video camera and a microscope. He packed the business in at the end. As far
as I know, the station is still sitting in his garage, waiting for him to
get around to eBay-ing it ...

I too handle the more 'standard' quad packages in a similar way to you,
using sometimes a very fine wire, and sometimes a shaped bit on the iron
that can heat all four sides at once. This is a fairly cheap, and very
practical way of doing it. Refitting is done using liquid flux, and the same
flooding technique as you. There are solder bits available that have a
special 'dent' in the end that holds a resevoir of solder that you can just
stroke along the pins, and just the right amount is capilliaried out onto
the joints. I haven't personally used one of these, but the same friend with
the rework station used to. I have a Roebuck long reach stereo microscope
that I use for the refitting. With a bit of practice, you can adjust to
soldering whilst looking through it.

As far as dealing with those very fine pitch LSIs goes, I think that unless
you are going to do enough of them to make it worth investing in the proper
kit, it's best to leave it to the manufacturers, and take the practical, if
less satisfying view, that in those cases, being a board jockey is the only
way to cut a profit from the job ...

Arfa
 
I

ian field

Jan 1, 1970
0
Hi;

I could use a bit of direction here. I have a RDA9330H to change, small
44 pin IC. Now I can get this done, just don't drink too much coffee
before work. Thing is, I saw other chips on the board with only ½ the
space between the pins and I am wondering how they are changed.

I have heard of heat guns, we have a magniying glass, but I need more
of the nuts and bolts of the process. I have changed a few LSI chips,
but the technique was less then optimal.

I cut the leads off the chip with a razor. Broke it off the glue, and
then painstakingly removed the bits so the new chip would seat
properly.

After tacking the new IC at opposite corners I flooded the sides with
solder, then wicked off the excess. This actually worked a bunch of
times on like the 44 pin QFP (I think) package of the TDA9330H. I
remember doing a bunch of them in Hitachi built camcorders. The digital
servo IC lost the phase lock for the capstan, and handled by the freq
lock alone caused massive wow and flutter. I had three or four of them,
after they were in top notch mechanical condition, they still had the
wow and flutter. It had two different pins for the phase and freq lock,
and they were not integrated exactly the same into the capstan control
voltage.

I did those differently, I used a guitar string for removal. I am not
worried about changing this 44 pin QFP. I am worried about the other
ICs on the board. Some of them pins got a mighty fine pitch. What do
you all do ? is it a hot air gun, or are we destined to become board
jockeys ?

Just figuring things out, a heat gun would soften the glue. Enough heat
would melt the solder and you just lift it off. Then, getting the new
IC aligned wqith some sort of jig, with downward pressure you should be
able to make it flow.

Even if this becomes feasible, we are not talking BGA ICs here. On
those I simply don't know.

Thanks in advance.

JURB


If you don't have all the gear and have to resort to using regular tools,
the fine pitch SMD chips can be easily removed by shearing the pins off
close to the chip body with a sharp blade like a Swan & Morton scalpel -
very great care is required not to score any print tracks under the pins so
practice on scrap boards until you're sure you can do it right every time!

The severed pins can be removed by flowing them off with solder, spread some
new solder along the row of pins and allow to cool so you can upturn the
board without running molten solder onto other components. By working the
board from below you can wipe the solder off the pads, the surface tension
will gather up all the pins, if you work over the wastebasket you can let
the blob of solder with all the pins in it drop into the bin.

The pads can be prepared for the new chip with solder wick braid, once you
have the new chip tacked by a few corner pins flowing a bead of solder along
the row of pins with the tip of the iron is the best way of not getting into
a struggle with it. Once all of the pins are flowed the excess solder can be
stroked off the pins by working upside down again - but even greater care is
required at this stage to avoid whiskering and getting solder on the pins of
other chips nearby! Also use plenty of fresh flux and clean with flux
remover afterwards so you can inspect for bridged pins!
 
Top