Solder Lead free?

In my limited experience with hand soldering on micro-sized circuit board pads, adding any additional solder greatly increases the chances of creating short circuits from excess solder remaining on the pins or pads.

A small amount of liquid flux is adequate, and I mean barely more than a slight trace of flux, because a drop is way too much, and will prevent good visibility. I generally use a toothpick with a little liquid flux on it, but much of it wiped onto a scrap of paper to leave just a thin coat of flux on the toothpick, then dragging the toothpick along one side of the IC, followed by a close inspection to see that a tiny amount of the flux is on each pin or pad, and then proceed to apply flux to the other sides of the IC.

I can't work on items that small anymore without magnification and very good lighting, and wouldn't attempt it without a good magnifier lamp, even with great eyesight.

Just touching a clean, hot soldering iron tip on the connection is normally all that's required for complete reflow of the existing solder. If there is excess solder on the iron's tip, it will likely cause problems.

With enough magnification, it's easy to determine if the proper reflow has been accomplished. If any of the connections appear to have too little solder for a reliable connection under close inspection, then it may require the application of a very slight amount of solder. Adding the solder can be tricky, but remember that it's probably going to be easier to add too much, than it will be to remove the excess, so just wet the iron's tip enough to get a little solder to transfer to the connection. The liquid flux will insure that transfer takes place.

I would use ordinary flux core 60/40 solder on the iron's tip, or a very small amount of paste solder, of the type intended for surface mount components applied to the pads (only if needed though).

-- Cheers, WB .............

many thanks.

One last question.This flux liquid is acceptable?

Regards

If the correct amount of liquid flux is on the job, then relatively huge quantities of solder can be added in via the iron's tip to 'drag solder' all the pins along a side pretty much 'en masse'. Only the correct amount of solder will adhere to each joint, pulled in by capillary action, and the liquid flux will do a remarkably good job of ensuring that shorts between pins do not occur. If they do, it is a very simple task to remove the excess solder causing the short, by the use of (good quality) desoldering braid. I agree that good light and high levels of magnification are needed to be able to do the job successfully. From the pictures in the links, that chip doesn't have a particularly high pin density, so should not present too much of a problem to resolder to the experienced hand.

The board was probably originally constructed with lead-free solder, so strictly speaking, lead free should be used for the rework. However, in this case, I think a much greater chance of success will be stood, by using conventional 60/40 leaded solder. Probably wouldn't be a bad idea to wick off as much of the original solder as possible, before adding new solder in.

Here is an excellent video of soldering technique, which gives a good demo of drag soldering, and use of desolder braid

Arfa

The product you asked about isn't liquid, it's a paste. I prefer liquid which comes in bottles, and is also available in pen applicators. The pens may dry out, but liquid rosin flux in a bottle can be thinned with denatured alcohol if it becomes too thick with age.

Paste flux will probably work fine, but may leave more of a mess to be cleaned up, if it can't be applied in very small amounts.

The SMD paste product I referred to is flux and powdered solder combined together in a syringe cartridge, or small jar, and it works well for reflowing existing soldered connections.

The close-up pic of the OP's Maxim 1987 shows that the package doesn't have long pins extending from the body of the IC, as the ICs in the training video do. So, if a solder bridge occurs, it might possibly be under the edge of the IC.. and maybe not easy to see or remove.

I didn't go to Maxim's site to look up the style of pins on that IC, but they appear to be very sshort, and I would consider 12 contacts within the width of a screw head to be a fairly fine pitch for anyone that isn't experienced at soldering small contacts.

I noticed that the training board solder pads aren't connected to real circuit traces or components, so it's not really the same as repair work. There doesn't appear to be any obstructions or tall components near the training board ICs, so it looks very easy, since there is nothing to impede the iron or hand motion.

-- Cheers, WB .............

That doesn't matter. Some fresh RMA liquid flux and a drop of fresh solder, un gently along the row of the pins will remove most bridges, anywhere along the length of the pins, with just a little practice. Just make sure the solder bridge is above the pool of molten solder, and that the flux has covered the solder bridge before you start. I've even removed loose solder balls that were trapped between an IC body and the pins that way.

The length or size of the pins doesn't matter, the technique is the same, and I don't see any nearby components that would get in the way of an iron being dragged sideways. If there are, where you can't see them, then they will be too close anyway to allow soldering 'by the pin' with the iron tip held at the appropriate angle for conventional hand soldering. In my experience and humble opinion, any attempt to rework an IC of this style using 'conventional' hand soldering techniques, is *much* more likely to result in un-recoverable disaster in the form of shorted pins, than drag soldering.

Your point about the pitch being fairly fine for anyone not used to soldering small contacts is valid, but then I wouldn't expect anyone not experienced *enough* to even try this rework ...

The package looks like a PLCC see -

You will see that the pins are of a perfectly conventional length and type, They are just wrapped around under the IC body.

Watch it being done at -

And here you can see both techniques being used -

but note the iron angle and space around the IC that's needed for 'conventional' soldering of these devices

Arfa

I'm merely making comments for the possible benefit of the OP and potentially others with limited or zero soldering experience.

Here is a 2006-2007 forum discussion of the same type of problem. There is a link for an exact replacement part, and as I suspected, there are no pins on that IC package. The metal contacts don't appear to be bent under the package, such as a PLCC package does. I've worked with PLCCs, and I was certain that the MAX1987 package wasn't the same as soon as I saw the close-up pic. I was also certain it wasn't a conventional QFP which also sit elevated above the board.

The Maxim package is described as Quad Flat No Lead at the end of the Curious Inventor 101 video, and they neglected to show one being soldered to a training board.

I wouldn't experience any aprehension in approaching the OP's motherboard reflow repair with only a clean soldering iron tip and slight amount of liquid flux (my original recommendation). I have a hot air station, but those aren't the absolute perfect method for many rework jobs, either. For that matter, the possibility of a cracked trace isn't impossible in a situation where opening and closing the laptop lid is causing the board to flex.

I'm not debating the drag method suggested, my comments were intended to be cautionary recommendations for a first-time or beginner at soldering.

For almost any applied material, it's nearly always easier to put it on, than it is to remove it. Not putting too much on eliminates the need to remove the excess, if that would take place. Many folks live by the rule of; if a little bit is good, then a lot is better. Maybe true for jam on toast, but not always good where equipment or machines are concerned.

Another note WRT training boards.. they don't have to work when completed, because they're not real circuits. Overheating may only be obvious if the pads lift off the 'glass board.

-- Cheers, WB .............

The notebook is HP Compaq NC6000 of the year 2003/2004.

Thanks

Regards

I really don't know about the solder composition on that board. The Lead-free initiative was to begin in 2006, I think, but that doesn't mean the HP board has lead solder.

Solder with lead will very likely work fine for the HP repair.

I wouldn't want to use lead-free solders for repairs, only because I'm completely confident of lead solders.

-- Cheers, WB .............

ok, many thanks.

Regards