METHOD FOR REWORKING LARGE DIL or SMD CLEAN FAST EASY

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simbo

METHOD FOR REWORKING LARGE DIL or SMD CLEAN FAST EASY

Postby simbo » Tue Feb 12, 2008 2:00 am

nice cheep method for reworking surface mount cleanly

you need

a bar from an electric fire
a multimeter
a 12volts battery high current small from a car say 90ampr or a 6v motorbyke type is better and smaller
or a 250watt switchmode psu using the 5v or 12v rail is ok for 5 amps or so easy
or i used a 0-30v psu @ 30amps total {bench supply}

a set of jump leads or some thick wires from a car lomb
bar of wood to mount the electric fire bar on if you intend using it as a resistor

a switch for the job or electric sewing machine controller {older the better} but not essential
tweezers to lift off the chip
or a sucker like a kids toy gun fires



so
you simply uncoil a few turns {i used 1ft of wire} from the bar carefully
now connect the fly end to the battery negative using a clip and leed
make a square out of the wire the right size for the chip one turn and no shorts
then use a crocodile clip from the positive of the battery
now you can slide the clip up the bar till the wire starts to get redhot
then switch off and ready the job
use the tweezers to lift off the chip
or the sucker and stick it firmly on with a lick and place the square loop round over it

you dont !!! need to touch the wire to the pins atall
just place the square slightly larger than the package round it
and turn it on
the red hot wire will with indirect heat melt the pins solder and the package simply lifts off

resoldering this way is also a perfect job every time and takes about 5mins total per chip change

dont !!!! turn it on while its round the chip and toughing the pins atall..
or you could fry the chip
this is important !!!! and could render a chip you want to keep useless if you do turn it on while connected round the target ic

a few old boards to practice on helps {i used 386 boards first time}
youll soon get the hang of it
your looking for about 2-3 amps use from the battery no more

so a 5 amp fuse inline

few tips
----------
the bar has to be fairly new so the wire isnt to corroded etc
or.... best use a foot switch from an old electric sewing machine
infact you can also use this as a controller for heat level as most its just a sliding wire resistor inside it

double check everything before turning it on last thing you need is a fire
a current meter inline and also a fuse is advised last thing you need is boiling acid explosions or warped plates etc melted plastic
this method is 100% guaranteed to remove the chip clean
then you need only re-dress the tracking you can use again the red hot wire and applying it above the area will flatten out the tracks evenly
instead of solder peeks left from the lift off stage

quick spray of flux spray and solder on the new ic using a fine pencil tip iron in two or four places before applying the heated wire again
to do all the pins at once is a cool move
then double tripple check all your work !!!!

i bought a year ago an smd rework station and wish i didnt spend 150 quid on it
but i still prefer this method for the higher densisty designs of package
even changing the controllers on old boards 80pins per side is easy
i just use the rework to resolder them now its faster and safer if there quite tightly grouped pins

you can use a small rod of bamboo you can also use a bit of the old bar as they are hollow
to run the loop thru for tightning it up etc...

youll need to mount a small glass beed at the end of it if you used bamboo
and also insulate the wires inside it using some of the white wirecover
sleaving you find in electric fires another thing is to twist two or three strands of the wire together
to form a bigger area for fpga chips with big pins

it will use a little more current but its worth it for the heatup staying power

this way you can have an ajustable loop and a usefull tool for the job.....
and make several varietys of loop


EASY this way .... for sure !!!!!



method to rework large dil packages and also headers like the floppy safely

without cutting them off or cooking them or the tracks etc....
like 68000 or shifters controllers etc...
you need to make two triangles from bifilar wound resistance wire {as above}
like coat hangers if you use one strand it will sag and never be flat
what i do is cut two equal lenghts about 50cm long
and use a speed controlled drill to wind them very tight together
this way you get a stifer element

you need !!!! to run these in parallel connections
as this distributes the load
and you dont end up with a bright spot on the wires
in there very center so its basicaly two elements
any old psu from a computer is fine for this and use the 5V supply or 12v

{several wires from it {red}} and a resistor made as above
lots of people have vast problems with the 40 and 80 pin dils to change them
even to try to desolder them is a nightmare using any sucker or wick tool

so you can see that making two triangles is better for the hot wire method
and bifilar is stiff and hotter
i can take an 40 pin per side dil 68000 cpu
out in about 20 - 30seconds heat
then clean its holes one by one using an iron


or !!! heat it up and lift drop the board to a thin damp sponge below
to clear them all at once

you may need to try to find the white china fire element that has two holes that run the lengh of it
instead of the single cavity
anway the same method applies
heat up your jig over the two rows and use an ic extraction tool or some bent over {adjusted } tweezers
to carefully lift off the dil once the pins come up to melting point
and a little after as it takes time to melt thru the plating
dont worry if the sides of the package get hot
a big problem with blowers is they stress the ic substrate too much
and damage the silicon

note on floppy headers

usualy i just cut the old one down and its the method i recomended till tonight
i tired out three trianlges set appart 5mm from each and all mounted in parallel circuit
i used some fire clay putty i made up basicaly you use this stuff to line ovens
and i simply squashed a small blob each end
and fired it up for a few mins to cure the putty then sanded it a little

so... using three inline i was able to lift out the floppy header clean as a whistle first cook

ive never managed to do an excelent job any other way till now with this header

usualy you atleast pull out a thru taking the bent pins out you chopped down

so few stats
i used three 2 core twisted wires in trianlges and a bit of china bar,,
i used a 250watt computer switched mode psu and the +5v rail
and a resistor made from the bar of a fire and a crock clip to adjust the heat
leave it about 7mm above the header and let it sit youll notice the solder melt wait a little longer and try to ease it out
with chips i always do them from the top with headers the bottom
so... it basicaly wiggle side to side and it fell out and a quick drop of the board and all the holes cleared

a job that used to take 20-30 mins and was messy reduced to 1mins totaly clean

tonight im happy i tried this out

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Re: METHOD FOR REWORKING LARGE DIL or SMD CLEAN FAST EASY

Postby Desty » Wed Feb 13, 2008 2:29 am

simbo wrote:a job that used to take 20-30 mins and was messy reduced to 1mins totaly clean

Yeah, maybe 1 minute to do the job, but now you have to collect:
  • a bar from an electric fire
  • car/motorbike battery?
  • a set of jump leads
  • bar of wood to mount the electric fire bar on (err, wood + electric fire bar = fire??)
  • (optionally) electric sewing machine controller

That seems like a bit of a treasure hunt just to avoid 19-29 minutes of work? :?: Unless it works perfectly/safely and you're doing it every day...
tá'n poc ar buile!

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Re: METHOD FOR REWORKING LARGE DIL or SMD CLEAN FAST EASY

Postby bullis1 » Thu Feb 14, 2008 3:35 pm

Desty wrote:
simbo wrote:a job that used to take 20-30 mins and was messy reduced to 1mins totaly clean

Yeah, maybe 1 minute to do the job, but now you have to collect:
  • a bar from an electric fire
  • car/motorbike battery?
  • a set of jump leads
  • bar of wood to mount the electric fire bar on (err, wood + electric fire bar = fire??)
  • (optionally) electric sewing machine controller

That seems like a bit of a treasure hunt just to avoid 19-29 minutes of work? :?: Unless it works perfectly/safely and you're doing it every day...


That's pretty much what I said but my posts about it got deleted. However:
This is a good and cheap method to use by the sounds of it, if you can find everything needed and have a place in your garage (or even have a garage at all) to set it up.

simbo

Re: METHOD FOR REWORKING LARGE DIL or SMD CLEAN FAST EASY

Postby simbo » Fri Feb 15, 2008 2:00 am

ok man

you two seem to have the ground in need to pick holes in a plated steel hull
in an empty dark room you would argue with the negative light

if you dont like the idea thats your issue dont read my posts and go use a solder ...sucker or wicks
and ill laugh at you again

go try take a 80 pin dil 68000 out
whole without ANY damage to the pcb or for that matter most ic.s
in under 1hr
plug it into an stfm socketed and boot up
when you can do this let me know
without using this method
using it
it take's me 30 seconds to extract and fit/boot
infact in 1hr i can collect every part i need to make it from my local area just on the street or an old heater in a pals house etc
ill take the 30 seconds pepsi style challange for outing a 68k and plugin and boot in a socket test anytime

then post me a picture of how you did it :wink:
and share your wisdom !!!

the parts and method i mentioned are fully accesable for zilch 0 nana
and cost nothing !!!!

if your compitant at all!! youll have a decent variable voltage psu say 0-30v
this control can be used to allow tempreture to be fully controlled so only the elements need made up
and there are many methods ive used to make them right im sharing at zero to you but years of graft for me
making then new now old machine work again without damage to them fixing them

its a tool a professional uses to get a job done right
and one i can guarantee knowone here uses except me and now others know..... perhaps them

there is always a few like you two
whos next ???? :contract:

if i wanted comments i would have asked for your opinion of the idea itself having used it

other than this its nothing more than a small sound from a big empty vessle and nothing else to do but try to
see the bad side in anything

few.... :coffe: however nothing ive not seen before
:roll:

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Re: METHOD FOR REWORKING LARGE DIL or SMD CLEAN FAST EASY

Postby Desty » Fri Feb 15, 2008 2:06 am

simbo wrote:there is always a few like you two
whos next ???? :contract:

if i wanted comments i would have asked for your opinion of the idea itself having used it

other than this its nothing more than a small sound from a big empty vessle and nothing else to do but try to
see the bad side in anything

Don't be a moron Simbo. I'll comment on something that's a good idea to support it, diss a bad idea if I think it's one, and ask questions about a post I don't understand. This is logical. You know logic, right?
tá'n poc ar buile!

simbo

Re: METHOD FOR REWORKING LARGE DIL or SMD CLEAN FAST EASY

Postby simbo » Fri Feb 15, 2008 2:15 am

no your comments are irrelevent and poised from an aggressive stance

this is a forum for discussing methods for doing a job correcly

with time ill add pictures and a video

please i will just lock the topic
as i dont wish to argue and im not going be reeled into the water by anyone

sorry ....

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Re: METHOD FOR REWORKING LARGE DIL or SMD CLEAN FAST EASY

Postby jd » Fri Feb 15, 2008 1:08 pm

Thanks for the info Simbo.

Please continue your 'guides' as they do come in very handy and many do appreciate them.

simbo

Re: METHOD FOR REWORKING LARGE DIL or SMD CLEAN FAST EASY

Postby simbo » Fri Feb 15, 2008 2:26 pm

well its nice to know others find the faq's usefull

i found in my junk box two 11watt and two 22watt and two 3watt very skinny and long types
the skinny ones you get also in old colour tvs

ceramic wirewound resistors

so i scrapped out there centers
and mount them together using some twists of wire and a spacer if needed

just a little apart so a few things are better by far


less risk of any scortch to the board as the heat is fully directed at the pins only the rest of the circuit each side of the chip doesnt get even warm

it takes now less heating to melt thru the platings

and its heeps safer from shorts of the elements to the pins of the chips and they are easily mounted to each other securly

also it allow you to sit the unit on the pcb but i add a couple of thin strips of foil just incase however...
its not essential and the ceramic doesnt warm too fast thru

its easier to get an extraction tool etc {bent tweezers} to the right parts of the ic
you can add a connector block to it and a cable and fix the elements in parallel
adding a switch to the top of you like is a nice addition
like a little oven

i was thinking about making a production of this
so i asked a chinese friend i have whos family run a business and he is looking into it

so maybe an off the shelf one is on the way

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Re: METHOD FOR REWORKING LARGE DIL or SMD CLEAN FAST EASY

Postby bullis1 » Fri Feb 15, 2008 2:42 pm

Simbo, you keep forgetting that I said you had a good idea twice. You deleted it the first time even. Be calm.

simbo

Re: METHOD FOR REWORKING LARGE DIL or SMD CLEAN FAST EASY

Postby simbo » Fri Feb 15, 2008 2:47 pm

chillout man Yellow_Hot_Colorz_PDT_41

i simply moved the topic to here and tidy'd it up as it is a guide and method and not really a question about hardware


if your sore becouse i deleted your post

im sorry but thats the nature of the job :wink:

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Re: METHOD FOR REWORKING LARGE DIL or SMD CLEAN FAST EASY

Postby bullis1 » Fri Feb 15, 2008 3:02 pm

Simbo you are the coolest dude. Let's all be chill together :coffe: :angel:

Let's now continue with the guide. I can't wait to see this video on YouTube. I hope you'll wear safety goggles Yellow_Colorz_PDT_11 because you might end up with no 'brows otherwise Yellow_Hot_Colorz_PDT_37

simbo

Re: METHOD FOR REWORKING LARGE DIL or SMD CLEAN FAST EASY

Postby simbo » Fri Feb 15, 2008 5:51 pm

ok
found out something

i got a pair of kitchen tongs spring loaded that open and spring close

added a stopper to give distance callibration and mounted the loops on its grabs at the ends
now i have two separate loops and on a nice spring loaded handle

i made the new element like this again a coat hanger shape thats been squashed flat to a upsidedown T shape
now i wound a 15 cm type 7cm each side 1cm gap
and with no need of clay ..
i can clamp it round a fpga chip just by making some 90deg bends to it

seems easier to use for fast work
and given the chance for tweezers to fit easier as it has some small gaps at the corners
still prefer the sucker from the plastic toy guns or a value seeter type from a car care shop {bit better} but it has issues tweezers cure
cost was £1.99 for the tongs they are stainless steel and the car shop had some 10 amp red black zip cable

this is good becouse you can just make the element straight to do dil's
and no need of added varients for up to 40 pins types still not every day you take out a really big dil

and also the chance to have a little foot on the end of the tong thats height can be adjusted
as a nice firming stance point for the exposure with out the shaking we oldies get

as usual if your not sure about it and dont know the calculation you may need to do it they are simple

V= I X R voltage = current X resistance
:. I = V/R :. R=V/I

W=I X V watts = current X voltage


the only two you need to stay safe and know what current youll draw in a dc system just knowing the voltage and resistance
and how many watts you use to do it etc..

then ofcourse its all one 1 amp = 1volts at 1 ohm {at one atoms at 1bar at sea level}

as a final point
you may need to use two fire bars in parallel for the adjustment rods as one will get quite hot on its own
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