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Few cents about the process: hot air soldering station, leaded stain, and some patience.

- Put some solder on the DFN and QFN parts. BGA already have (the balls themselves). This method works for small BGA (48 balls in this SRAM).
- Put some solder on the footprint. Here, an stencil (there are plastic stencils and manual systems to use them) would be useful, but we don't have it.
- Remove the excess of solder from the pads and components.
- Prepare the hot air soldering station with a low speed, medium volume nozzle, about 450ºC. In our case, we remove directly the nozzle. This point is important: a high air speed will move the part or even remove little (0603 and such) components if present (literally, blow them away).
- Heat up the board, as even as possible around the component, without the component, and trying to isolate thermally the board to avoid excessive cooling.
- Place the component accurately (the most difficult part, specially for BGA).
- Apply heat again.
- With a little plier or tweezers, move sligtly the component while applying heat, until one can see that the melted solder places the component in position thanks to the surface tension.
- Stop applying heat, wait until the board cools down.
- Aply some 'cold air' or move to another component.

I don't have any video, but could be interesting trying to do one. I will let you know if this happens.

Guillem.
"Common sense is the least common of the senses" Anonymous.

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Guillem, please be very-very cautious with these extreme temperatures (450°C)!
Personally, I do not need to use hot air of 260°C and above! Especially in multilayer (4 layers or more) PCBs...

Ali, this is a Reflow Soldering Guidelines AppNote from Altera.

The AppNote above has been a great help to me, since I recently had to remove a 17mm x 17mm FineLine BGA ("FBGA" with pads of 0.50mm diameter and 1.00mm pitch) chip, create the schematics of the PCB and finally reball & resolder the BGA back in place. Furthermore, in order to reball the FBGA package I used regular 63/37 alloy solder balls without a stencil, no-clean gel-flux and hot air of 210..220°C for about 60 sec, since I was able to be visually inspecting the reballing procedure.

Anyway, please let me describe the steps I take, using a hot air station.

In reflowing, there are three critical temperature points:
A. 150°C, where the flux begins to activate,
B. 183°C, where the leaded solder melts (Sn63/Pb37 or Sn62/Pb36/Ag2 alloys), and
C. 220..240°C that is the maximum component package body temperature (consult the component's data sheets).

These are the four phases of the reflow process, after having tinned the PCB/component pads/pins, having applied a thin coating of flux (or solder paste on the pads only) and having carefully placed and aligned the component in position:

1. Preheat the PCB around the target component to 140..150°C for 60..120 sec to avoid any thermal shocks of the PCB and/or the ceramic components. The flux has not been activated yet.

2. Activate the flux ("soaking" phase) but do not melt the solder, by raising the hot air temperature to 180°C for 60..120 sec. The flux activates and de-oxidises the solder.

3. This is the actual reflow phase, where the solder melts and solder joints are created. To prevent warping, bridging, and cold solder joints, keep the package body above the solder's melting point (183°C) for at least 60 seconds (60..150 sec) but do not exceed the maximum package body temperature.

4. Cooling down. The reflow stage is complete when the molten solder connections cool and solidify to form strong solder joint fillets. A fast cooling rate reduces the grain size of the intermetallic compounds and strengthens the solder joints. However, controlled cooling is important to reduce stress on the component body and minimize warping. Right after the phase (3) reduce the hot air temperature to 100°C for 30..60 sec and, finally, let the PCB alone to reach room temperature.

-George

I hope for nothing; I fear nothing; I am free. (Nikos Kazantzakis)

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George, the information I gave was for our attempt without reflow oven, where the hot air gun blow a very slow air and far from the board, in normal air, not inside an oven, thus thermal looses from the nozzle to the board would cool down many ºC.

Anyway, take my information with a grain of salt, since that was a simple (but successful!) attempt done many months ago, and my brain is not good recalling values.

A manual reflow oven would be fantastic for this kind of work, but we don't own one yet (perhaps within half year or so, it seems).

Guillem.
"Common sense is the least common of the senses" Anonymous.

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Guillem, neither do I have a reflow oven; nor I seem to be urgently in need of one, since I think I can do almost anything I need to, using a hot air rework station. A hot air station seems to be more than sufficient for local rework or for one-off jobs.

I realise that the hot air temperature drops down when blown from a distance. But I wrote that flat-package reflow soldering rework mini-guide above, to prevent any souls from using their hot air stations with temperatures or techniques (as carelessly advertised in some YouTube clips) that can cause permanent damage to components and/or to PCBs.

-George

I hope for nothing; I fear nothing; I am free. (Nikos Kazantzakis)

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Thanks for the info Guillem

Quote:

I don't have any video, but could be interesting trying to do one. I will let you know if this happens.

I'd realy appreciate that!

I love Digital
and you who involved in it!

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George
Thanks for your great info.
Would you kindly please share some video or photo’s? It’s one of my dreams to hand solder BGA parts!
I have only access to a hot air gun.

I love Digital
and you who involved in it!

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You are welcome, Ali.

I am afraid that I have not documented in any videos or pictures the hot air rework procedure, since using a hot air rework station is mostly a matter of practice. I have had, though, an interesting exchange of views about it recently with Steve (our fellow AVRFreak steve17) at this thread.

In a few words, you can purchase a hot air rework station for as low as €50 only (see the ATTEN AT858D+ Hot Air Rework Station) and using good flux (I personally prefer RMA or no-clean gel-flux) and leaded (63/37 or 62/36/Ag2) RMA or no-clean solder paste (that is flux with tiny solder balls in paste form) you can do almost anything! But it takes practice; you can experiment as much as you like by using older cell-phone PCBs that you are not afraid of destroying. Then you will become familiar with the hot air station settings of air temperature and volume/velocity, the solder paste quantity needed and the distance between the nozzle and the PCB.

In my experience, preheating the PCB area around the target component before, using the lowest possible temperature and a nozzle distance from the target component/ PCB of 3..8mm works miracles!

The only picture I have posted is of a Cyclone III FPGA after having it re-balled (i.e. restored the solder spheres on its pads after having it desoldered from the PCB and cleaned it from the old solder residues), in another discussions board under the screen name "A Hellene"; but it seems that this board is inaccessible right now, being in maintenance mode... You can retry accessing these links in a day or two.

I am also afraid that a hot air gun is not suitable for working with PCBs because a hot air rework station produces hot air of regulated temperature and volume/ velocity; for example, my unit regulates the hot air temperature in 1°C steps. By the way, the ATTEN unit above can be so cheap because it is a product intended for the Chinese market only; but, thanks to the slightly open market of these days, it can be shipped globally at this low price.

A quick search in YouTube can reveal a few clips about BGA rework and BGA reballing using a hot air rework station; but one should be very skeptical when seeing these people using temperatures of 280°C and above at these clips...

-George

EDIT: Ali, I've found a YouTube clip on the removal of a micro-BGA.
This is the translation of the Greek captions:
00:00: Initially, we protect any plastic components (using Kapton Tape)
00:46: I forgot to plug it in...
00:54: Cold air untill applying flux
01:39: The flux "spreads" when the PCB is preheated
02:27: In this case we can use any nozzle; using a circular motion the heat is applied uniformly
02:44: The BGA has been removed without even having the solder "balls" been disrupted

Though it is a nice presentation, using a preheater beneath the PCB, I am afraid I will disagree with the last statement, about keeping and reusing the old solder residues. I would wipe them clean from both the PCB and the chip using solder wick and reball the BGA component.

I hope for nothing; I fear nothing; I am free. (Nikos Kazantzakis)

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A hot air gun can work very well, if it's one of those more expensive models that can be programmed to a certain temperature and airflow. A normal one with one or two settings is only good to remove components.

I regularly use one to solder Samtec 1.27mm pitch horizontal SMD headers; one row of pins is unreachable for an ordinary soldering iron.

A 'true' hot air station can't do it. The volume/area of air is too small to heat up all 14 pins together. Probably it takes a special tip instead of the regular round one.

A plain hot air gun without precise temperature/air control is nice to strip paint and shrink heat shrink tubing, but blows way too hard for precision soldering work.

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Hi.. I am new in this forum. a regard to all the people of this forum .
I have a rework station hot air Honton HT-R490. however I have some doubts and not to know that it bends temperature to work with a processor bga smallest. 8 X 8 millimeters. can you help me? the processor is an infineon 337S3833, X-gold 61x. how HT I must plan setup of the station?

:?:

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Cross post alert.

Same Q here in a thread of its own, as it should be: https://www.avrfreaks.net/index.p...

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