Preventing Pad Lifts

I'm only coming at this from repair soldering rather than production and assuming you are referring to hand soldering. I would suggest the wrong soldering technique may be being used.

With a conical tip then the very tip on the pad and the bulkier part of the cone to the, in comparison, more massive pin. More heat to the more massive/heatsinky part of a joint and the rest tends to take care of itself

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Stay under 625 F. I seem to need at least that most of the time. use liquid flux, and only use higher heat on the larger pads. Cut off any parts before removing, and use some solder braid.

greg

Rob wrote in news:1179839486.343163.119380 @r3g2000prh.googlegroups.com:

Very dependent upon the type of solder used, and what kind of components and what type of boards you are working with.

By the way, there are printed circuit board repair kits. Google for them.

In the cheap electronics i dont think you can do much . I work on the cheaper stuff , basically brand new store returned items such as small stereos & such . Sometimes foils lift just by handling the board and pushing or tapping lightly on parts . I would say keep your soldering tips in good clean condition and dont heat anything very long . If you can get hold of the part first and pull on it while quickly heating the pads the part will pop out then very quicky use de-solder braid to clear the hole . Use lower heat irons . High heat can very quickly fry whatever holds the pads on .

I can only tell you from my experience (been there, done that), that too much heat for too long causes this especially when the iron tip is in contact with the pad. Heat the component pin first, then slide the tip to the pad to finish removal of solder. This seems to work best for me. Good luck.

I tend to only heat the pin with the iron and introduce the solder wire between the soldering iron and the pad so the melting solder,only, heats the pad. Unless it is a large ground pad or wide strip rather than a pad, ie substantial heatsinking.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

snipped-for-privacy@webtv.net (Ken G.) wrote in news:6278-4653023A-261@storefull-

An iron with a built in 'solder sucker' helps a lot.

Radio shack has an el-cheapo with a red rubber bulb that works well, or one can buy an expensive vacuum equipped desoldering station (with temperature controlled iron).

snipped-for-privacy@webtv.net (Ken G.) wrote in news:6278-4653023A-261@storefull-

My soldering training said that use of solder braid gets more heat applied to the PCB for a longer time,making pad lifts occur more. Same for SoldaPults. They specified the use of a temp controlled vacuum desoldering iron.

Yes. And everything clean and a good flux.

Never. Speed is the key.

"Charles" wrote in news:OtGdnZROZfdE9M7bnZ2dnUVZ snipped-for-privacy@comcast.com:

Not strange. The original solder could be 95/5 or 60/40 or 50/50 even. adding some good eutectic solder will make the old solder melt faster and stay liquid longer.

bz wrote in news:Xns9938C1AA4E299WQAHBGMXSZHVspammote@130.39.198.139:

For that matter,you could use ChipQuick,and desolder at VERY low temps. ChipQuick solder melts at 160degF,IIRC,so the combined melt point is IIRC,

Yes. You should almost 'paint' the solder on.

All of the paste solder we used in our reflow ovens was 80/20.

Also, leave a 1/8" to 1/4" of used wick at the end to quickly transfer the heat into the joint. Put the solid spot on the joint, and apply the iron. When it stops its capillary action clip it back, and continue. A small bottle of liquid flux to dip it in, between uses is also handy if you don't have a squeeze bottle with a large bore hypodermic needle to dispense the liquid flux.

Now that I have a decent digital camera, I will see about making a short video to show the techniques I used in manufacturing to rework boards on the module test line. In four years I only damaged a couple pads, and most of them were caused by the company's refusal to let me put the stereo microscope on a bench, instead of a cart.

I could desolder and reuse 144 legged ICs. i agree with the liquid flux, I prefer Kester industrial RMA flux. i think the last bottle was type 1544 RMA.

I used 750 to 825 degrees on my three different irons. They were calibrated every three months, and checked daily for high resistance between he ground pin and the tip. Anything above three ohms required the tip to be removed, and the shank cleaned with a soft brass brush to bring the resistance back down. Once an iron reached three ohms, it could go quite high and cause ESD damage.

Depending on what type of component you are removing the heat, time and tools are all important. The general rulle its least amount or heat in the least amount of time with no downward pressure and lots of patience, thats what I preach to my students. As with all processes the tools need to do the work and not be used improperly, which in soldering means avoid at all cost pressure, soldering should not be pressure activated. Pressure is what gets us in trouble when using poor maintained equipment or improper techniques.

For most lead bearing solders, which is most likely what you are dealing with, you should always start with a temp around 600 f and modifiy from there. If its lead free you will need to up that slightly, but not dramatically.

If you just do a lot of repair on the cheaper boards, I would suggest looking into the circuit repairkits/techniques, some of the kits will be better than the original when used correctly and again good well maintianed tips and tools are key.

Anyway thats my 2cents email if you have questions or specifics of the application you would like help with.

Ruffin Blackard IPC Instructor

Depending on what type of component you are removing the heat, time and tools are all important. The general rulle its least amount or heat in the least amount of time with no downward pressure and lots of patience, thats what I preach to my students. As with all processes the tools need to do the work and not be used improperly, which in soldering means avoid at all cost pressure, soldering should not be pressure activated. Pressure is what gets us in trouble when using poor maintained equipment or improper techniques.

For most lead bearing solders, which is most likely what you are dealing with, you should always start with a temp around 600 f and modifiy from there. If its lead free you will need to up that slightly, but not dramatically.

If you just do a lot of repair on the cheaper boards, I would suggest looking into the circuit repairkits/techniques, some of the kits will be better than the original when used correctly and again good well maintianed tips and tools are key.

Anyway thats my 2cents email if you have questions or specifics of the application you would like help with.

Ruffin Blackard IPC Instructor

I DID NOT WRITE ANY OF THE QUOTED TEXT AT THE TOP OF THE PREVIOUS MESSAGE. I have worked in electronics for over 40 years, and did my own surface mount rework under a stereo microscope. Your recommended temperature was too low for the work I was doing, because I did a whole row of pins in one pass, with the corner of the tip. I used .015" Multicore rework solder, but the reduced contact area required over 700 degrees to allow proper wetting and flow on the leads. This was for items that are in orbit, BTW.

I am very familiar with the IPC, your publications were all over the QC inspection tables at my last job. They couldn't tell which pins I had hand soldered, compared to the joints done by the new Heller reflow oven, until I showed them the proper angle to look at them to see that the new joints had more shine than the reflowed joints. (less time for oxides to form) The running joke was that if they couldn't find my work, they HAD to stamp it off.

I was teaching proper rework soldering technics in the mid '70s at a defense plant that built military radios. The assembly people who soldered had all been certified to NASA standards. It was a union plant, so I rather enjoyed the angry stares from the union steward while a final test QA inspector taught new rework methods. As usual, they were using too little heat to do the job at hand. There were no large irons allowed on the production floor, and they were using fixed temperature Weller soldering stations so it took two irons to get any reflow. A third one would have been handy, but they were not allowed to move anything between work stations.

I have to agree with Mike. I found 700 degrees F to work best in my 35 years soldering. Most of my work has been through hole and very little surface mount.