Hi Steve-
Destroying the connector is a good idea, as long as the process doesn’t result in a bunch of particulate contaminants. Even after that, I'll bet that cleaning out the holes is darned difficult.
You can get a lot of the capability of an Air-Vac by kludging together a bunch of cheaper stuff. (Any SMT assembly area without some kind of controlled rework process must be a frustrating place to work.)
My building didn't have a rework system, so I set up a pretty passable system using a Hakko FR-803, an old microscope boom mount stand with focus adapter, a controlled temperature hot air pre-heater, and a pretty cheesy board holder. I happened to have an old Zephyrtronics for the pre-heat, but you could easily take a feedback controlled hot air gun and add some ducting to get it to the back side of the circuit board. The hardest part of putting it together was building a clamp which holds the hot air tool in the microscope focus ring. Anyone can probably set up a real nice system for about $2500 in new/used parts and a day of fooling with it. It doesn't have all of the bells and whistles of an Air-Vac, but frankly, that company has ticked me off by not supporting older equipment. And I'd wager the repeatability of this kludged system is on a par with the more expensive stuff.
Anyway, that system probably wouldn't completely solve your present problem because it is hell to get the solder out of all of the holes. In the days before surface mount, you could heat the crap out of a board and smack the board on the rim of a trash can and clear 95% of the holes. But with a bunch of surface mount around the area, that's not an option. Believe it or not, I once programmed our Excellon drill to clean out holes. You probably don't want to go there!
Once, I had a bunch of work to do like what you're talking about, and I tried to build a huge version of a solder sucker. I built a little 5 sided aluminum box which just fit around the bounds of the connector, and put in 3 quarter inch vacuum lines into it, gasketed around the board contact perimeter and set it on a hotplate. I then used a thermostatically controlled heat gun on the top of the board to get everything melting (cut up a soda can to limit the topside preheat area). It needed a local vacuum reservoir to provide the capacity to the quarter inch lines, and I used a foot operated dump valve to create a sharp dump profile.
That system worked pretty good for clearing the holes, and the adjacent SMT parts were fine, but there were a bunch of electrolytic caps in the area too, and some of those would boil and vent when I was doing that operation.
Rework is NEVER easy!
Wayne
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Tuesday, May 05, 2015 5:45 PM
To: [log in to unmask]
Subject: Re: [TN] Chip Quik Removal Alloy
Hi Dave,
In a past life this was used to rework through hole connectors on boards that were approaching .300" thick and 40-layers, but that was using the leaded version of the Solder Quik. The contamination of final solder joints was minimized by re-filling the barrels with the final solder and then extracting it to dilute the concentration of any residual solder that might be left behind.
The issue that I have now is that we have a couple of boards that have lifted connectors that need to be flush to the board. They're 42-pin Samtec ESW-122-12-G-D connectors that run down the center of the board and, there's SMT IC's all around them. I don't have an AirVac or anything like it to rework the connectors. All we have is a heat gun and a solder extractor. The board is constructed in such a way that it just sucks and dissipates the heat away from the connectors. We have a very good rework lady here and she is just pulling her hair out trying to rework these things. She had to remove a smaller connector and wound-up destroying the connector and pulling it out pin by pin. That connector didn't have all the SMT around it that the 42-pin ones do, so I'm trying to help her rework these boards without pulling a barrel or delaminating the board.
It's only been a few times that I've run across a .062" board that dissipates heat like this...it's really weird.
Steve
On Tue, May 5, 2015 at 2:54 PM, David Hillman < [log in to unmask]> wrote:
> Hi Steve - assuming you are using SAC305 solder, then any element(s)
> you "add" to the SAC305 solder joints that has a lower melting
> temperature will allow you to remove the connectors at a lower
> temperature. Since indium melts at 157C, you would lower the melting
> point of SAC305 to something below 217C depending on what the final solder composition ends up being.
> And depending on the alloy phase diagram, you could end up being even
> lower if specific alloy combinations are formed. The bigger issue is
> that if you don't get all of the "new" solder composition off the pads
> or the connector (if you planned on reusing it) as part of your rework
> process, then you will have unknown solder joint integrity which may
> or may not be appropriate for the product use environment. Food for thought.
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
> On Tue, May 5, 2015 at 1:07 PM, Steve Gregory <[log in to unmask]> wrote:
>
>> Hi All,
>>
>> Do any of you know if the Chip Quik Removal alloy (Tin 30%, Bismuth
>> 56%, Indium 14%) works with lead-lead free solder?
>>
>> We have a board here that has to have some connectors reworked that
>> are absolutely a bear to remove and I was wondering if it works with
>> lead-free solder?
>>
>> Steve
>>
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