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Soldering Upgrades in my 42s
Message #1 Posted by DavidShenk on 20 Oct 2009, 10:42 p.m.

I finally bought a soldering station (Aoyue 937+ ) that seems to get good reviews but is inexpensive and has temperature control. The plan is to use it, among other things, to upgrade my 42s memory.

[Deeeeep Breath]

I took my beloved 42s apart the other day and didn't have that much trouble removing the 8K chip. The tip that comes with the iron is very pointy. Now my problem is the installation of the new chip. From some videos I've seen online, if the tip is too pointed, the solder won't be right at the end where you need it. This seems to be my issue. Of course, my poor 42s isn't working now in it's current state.

[Holding back tears]

Can anyone recommend a soldering tip or tips that they use for this type of work? Also, is a temp of 625F or so sound about right?

Any help in this area would be appreciated. Dave

      
Re: Soldering Upgrades in my 42s
Message #2 Posted by Vieira, Luiz C. (Brazil) on 20 Oct 2009, 11:19 p.m.,
in response to message #1 by DavidShenk

Hi, David;

I have already upgraded about eight HP42S (three were my own, one was gifted) and I remember that after removing the 8KB RAM IC, soldering the 32KB RAM IC was relatively easy. I am sorry (Im no native English speaker), but by pointy, do you mean the tip of the soldering iron is too thin or thick? Could you add a picture of it? If you had no trouble removing the 8KB RAM IC, I thought you'd have no trouble using the same soldering iron to set the new RAM in place.

And if you decided to stop and ask for help prior to go ahead, then you have chosen the best option (no need to worry about the HP42S without the RAM IC; just do not try powering it up now...).

I hope other guys have better directions, though.

Success!

Luiz (Brazil)

Edited: 20 Oct 2009, 11:23 p.m.

            
Re: Soldering Upgrades in my 42s
Message #3 Posted by DavidShenk on 20 Oct 2009, 11:38 p.m.,
in response to message #2 by Vieira, Luiz C. (Brazil)

Hi Luiz, Yes, the tip seems to be too thin. Tapered too long, I guess. When I melt solder on the tip, the blob seems to move back a bit, away from the very tip. Touching the dry tip to the pin does nothing.

The tip shape is pointed like a pin or needle. I'm thinking that a chisel or beveled tip might work better.

Dave

                  
Re: Soldering Upgrades in my 42s
Message #4 Posted by Hal Bitton in Boise on 20 Oct 2009, 11:52 p.m.,
in response to message #3 by DavidShenk

Hi David,
That thin tip may be running a little cold. Try bumping the heat control up and see if the tip will draw solder then.
Best regards, Hal

                        
Re: Soldering Upgrades in my 42s
Message #5 Posted by DavidShenk on 20 Oct 2009, 11:57 p.m.,
in response to message #4 by Hal Bitton in Boise

That is a good idea, I'll have to go and try that. My problem just can't be operator error ;)

Dave

                  
Re: Soldering Upgrades in my 42s
Message #6 Posted by Vieira, Luiz C. (Brazil) on 20 Oct 2009, 11:59 p.m.,
in response to message #3 by DavidShenk

Hi, David;

I am not if I understood this:

Quote:
When I melt solder on the tip, the blob seems to move back a bit, away from the very tip.
When I am soldering electronic components I do not use the soldering iron tip as a means to put solder in place. Instead I touch the surface to be soldered (component and PCB) with the tip of the solder stream (is that correct?) and then I touch both the solder and the surface to be soldered at the same time with the soldering iron tip. I had to acquire practice by soldering many simpler components (more than 25 years ago...) prior to make sure I was doing it correctly, and the smaller the surface, the faster we must be. SMDs are the worst 'common cases'.

I have no videos nor pictures to show the way I solder, sorry! And pPlease, if this is not the case and you have prior experience with soldering, forgive me. Maybe I understood it wrongly.

Success!

Luiz (Brazil)

Edited: 21 Oct 2009, 12:01 a.m.

                        
Re: Soldering Upgrades in my 42s
Message #7 Posted by DavidShenk on 21 Oct 2009, 12:29 a.m.,
in response to message #6 by Vieira, Luiz C. (Brazil)

Luiz,

I think that was my next question. In the videos I've seen soldering SMDs, they were doing the opposite of what you just described (here) . They put flux on the pins and a little solder on the iron, then touched the tip for just a second and the solder flows over and makes the connection. They were doing several at a time and it seems so easy!

I'll have to try it the way you described, but I need to get some fine solder wire first. I know this is how you solder more traditionally sized components, but I didn't realize you could use the same technique on SMDs.

I have only casual soldering experience and have never worked with anything so small, so any tips or critique is appreciated.

Dave

                              
Re: Soldering Upgrades in my 42s
Message #8 Posted by Vieira, Luiz C. (Brazil) on 21 Oct 2009, 12:49 a.m.,
in response to message #7 by DavidShenk

Hi, David;

at this very moment, I'm saving the video to see it later. Thanks.

You are correct with the appliance of the technique I mentioned to bigger components. As you also mentioned, if they are using soldering flux in the video, this means even faster soldering.

I did not see the video yet, so can you tell me if they applied the technique to a PCB with 'virgin' contacts, i.e., a PCB that had not yet been soldered? I have never soldered SMT components for the first time, instead I replaced many. So, there is always a thin coat of solder in both the component and the PCB. IN this case, I position the component and touch the tip of the soldering iron in two opposed terminals first (I.C.s in this case). Then I solder the rest of them the way I mentioned. I use fine solder when dealing with SMDs, but when the solder spreads to neighbor terminals, I use the 'solder trap' (cannot remember the name of the 'wire mash to remove solder' in English, sorry) to remove the excess of it.

Ill see the video and post later, OK?

Cheers.

Luiz (Brazil)

Edited: 21 Oct 2009, 12:52 a.m.

                                    
Re: Soldering Upgrades in my 42s
Message #9 Posted by DavidShenk on 21 Oct 2009, 1:02 a.m.,
in response to message #8 by Vieira, Luiz C. (Brazil)

I am curious to see what you think of the video. They did a very good job shooting it. I think in the examples they are using virgin boards and new components.

After I removed the 8K chip, I did go back over each pad and level the solder before placing the new chip on. Then I was able to solder down two corner pins, but that was about it.

I think the solder trap you're referring to is called desoldering braid or desoldering wick? I do have some and have already had to use it.

Dave

                                          
Re: Soldering Upgrades in my 42s
Message #10 Posted by Vieira, Luiz C. (Brazil) on 21 Oct 2009, 1:24 a.m.,
in response to message #9 by DavidShenk

Hi, David;

the video is indeed vary good and has very important information. The way I usually solder SMT components is a mix of the techniques shown for the PLCC and the QFP. I actually use the residual solder that remains in the tip of the iron to allow the existing solder in the PCB and the components terminals to melt, and after some terminals are joined together I use a bit of solder to go ahead with the other terminals. I do not use some techniques shown in the video, like using a big amount of solder them removing the excess with this purpose, but in some previous industrial SMD soldering, the whole PCB with glued components were dipped into liquid, high temperature solder, so... what the heck do we know!

I agree with you, they are using new components and virgin boards, but the new boards seem to come with a coat of material in the soldering tags (terminals?) that I cannot identify. Maybe it has the same properties of the solder and helps soldering.

And yep, I was trying to mention the desoldering braid, or desoldering wick. Thanks.

I think the video gives enough guidance to a successful soldering. Can you find some old, not working PC board or daughter board, like slow modems or audio boards, that you could remove and re-solder SMDs for the sake of 'skill enhancement'? Chances are that youll find your best, successful way of soldering. I'd bet that!

Success!

Luiz (Brazil)

Edited: 21 Oct 2009, 1:25 a.m.

                                                
Re: Soldering Upgrades in my 42s
Message #11 Posted by DavidShenk on 21 Oct 2009, 2:12 a.m.,
in response to message #10 by Vieira, Luiz C. (Brazil)

I do need to practice my technique on some scrap electronics before I work on my 42s again. Good idea! It appears that there are several different ways to do this, so I'll have to practice and see what works for me.

Thanks for all the help. Dave

                                          
Re: Soldering Upgrades in my 42s
Message #12 Posted by Eric Rechlin on 21 Oct 2009, 1:40 a.m.,
in response to message #9 by DavidShenk

Surface mount soldering is actually very easy. You do not need desoldering braid for cleanly soldering surface mount chips.

Just put flux on the board (something like Kester 186-25 is my favorite, but Kester 979 is good if you prefer no-clean flux), and position the chip.

Put a big blob of solder on the tip of your iron. Touch it to one corner of the chip. Now drag the tip of the iron (which presumably still has a blob of solder on it) across the pins on the opposite side of the chip. You'll solder them all at once, in a single stroke, and the flux will prevent the pins from sticking together.

Now use the remaining solder to do the other side of the chip, and re-stroke either side if there are any shorts.

You should be able to do a 10-20 pin chip in well under 30 seconds with this approach.

Edited: 21 Oct 2009, 1:41 a.m.

                                                
Re: Soldering Upgrades in my 42s
Message #13 Posted by DavidShenk on 21 Oct 2009, 2:15 a.m.,
in response to message #12 by Eric Rechlin

Thanks Eric,

I'll have to try it. I've seen this in a video, but it almost seems like magic. I'm trying to daintily do each pin when they can be done so quickly. I have to practice on some scrap boards first.

Dave

                              
Re: Soldering Upgrades in my 42s
Message #14 Posted by Garth Wilson on 21 Oct 2009, 1:38 a.m.,
in response to message #7 by DavidShenk

Quote:
In the videos I've seen soldering SMDs, they were doing the opposite of what you just described (here) . They put flux on the pins and a little solder on the iron, then touched the tip for just a second and the solder flows over and makes the connection. They were doing several at a time and it seems so easy!
What kind of package are you trying to solder? I haven't tried any PQFPs, but I've done a few large SOICs onto SOIC-to-DIP adapters and found they were even easier than the video shows. I found that with a lot of flux, you can just go down the row of pins and flood the whole row with solder, making bridges everywhere with a large tip and large-diameter solder, then hold the board vertically and go down the row again, from top to bottom, and all the excess solder will come off the board and stay on the iron. There will be the same amount of solder on each pin, and it will be smooth, and there will be no bridges. You don't need any solderwick. You do have to clean the flux off when you're done though.

Concerning the temperature: There's a lot of unnecessary worry about this. In my work in the mid-1980's I occasionally had to do thermal scanning of power transistors in operation. In the extreme situation, I saw transistors actually operating at many hundreds of degrees C (not F). Of course they wouldn't last very many hours doing this, but it did not destroy them. I like to use a very hot iron to solder, as this allows you to get the joint up to soldering temperature more quickly and be done before the inside of the part gets so hot. This is especially important with things like mechanical switches that have plastic parts. A hotter iron is less likely to melt the switch before you're done. I've seen our production people do more damage with expensive, low-temperature irons than with the 950-degree F uncontrolled ones.

Edited: 21 Oct 2009, 1:38 a.m.

                                    
Re: Soldering Upgrades in my 42s
Message #15 Posted by DavidShenk on 21 Oct 2009, 2:21 a.m.,
in response to message #14 by Garth Wilson

Hi Garth,

I'm trying to solder a 28 pin SOIC. I'm going to try the technique you suggest on some practice boards and see how it goes. Thank you for your comments about temperature. I have a feeling it has a lot more to do with technique and skill than sticking to a specific temperature. I probably didn't start with easiest thing to learn with...

Dave

      
This is a toy, not a tool.
Message #16 Posted by Frank Boehm (Germany) on 21 Oct 2009, 8:51 a.m.,
in response to message #1 by DavidShenk

Please keep in mind that Aoyue is not exactly a manufacturer of quality tools - this is what makes your soldering tip "crappy". A single tip from PACE, WELLER or ERSA already costs a good fraction of your whole soldering kit and actually is more high-techy than it seems. Be assured, the solder sticks to the tip on these ones ;) Maybe the tip could be replaced by a better (branded) one, that should help on your soldering project.


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