iMac G5 stuck component leads

[duffling]

Hi All,

A question for anyone who has come across this issue.

Removed most of the caps no problem using my Aoyue 474 desoldering station with little damage to the pads.

However several of the component legs broke off in the process due to lack of wiggle space near the G5 heat sink.

Have tried reflowing solder and desoldering the point in question, sewing pin pushing from the other side while desoldering and heat applied for a short time on both sides none worked.

Did have limited success using Chip quick and sewing needle on one of the points.

The legs are well and truly stuck and I don't want to risk too much messing around as I know it's very easy to damage the solder pads.

Would careful drilling using a smaller diameter carbide drill work to clear the cap hole? or is this too risky on multi layer boards.

Any ideas would be most appreciated.

[Scenic]

Re: iMac G5 stuck component leads

try to push them through with a toothpick while heating the pads from the other side (with extra solder+flux added)
usually works better than a metal needle, cause the needle also heats up, drawing heat from the stuck pin (and burning your fingers if you didn't put a "handle" of sorts on the needle somehow )


i used a screw terminal as a handle on the metal needle.. works reasonably well

[Toasty]

Re: iMac G5 stuck component leads

No, I do not recommend a drill bit be used on these. The vias are plated through from one side to the other. A drill bit would remove that plating.

Use a 60/40 or 63/37 rosin core, *leaded* solder with additional flux as Scenic recommended. You want to re-load the holes with a lower temp solder to make extraction easier. The lead free solder that these are manufactured with requires too much heat and these are delicate pads.

I've found that pre-soldering each cap with fresh solder before I go to extract them makes it a lot easier. Yes, there is always 1 PITA on the output side. It has heavy traces (ground) on both sides and just sucks the heat away.

It also sounds as though the desoldering station is not running hot enough or perhaps you're being cautious and don't have it cranked up far enough. I recommend the larger bore tip be used. It has a higher heat transference because the contact surface area is much higher. Make sure she's got a clean tube and the filters are clear and moistened as recommended.

Toast

[Toasty]

Re: iMac G5 stuck component leads

~time limit~

EDIT: Just looked up the Aoyue 474 info. It simply does not get hot enough for lead free desoldering. Especially on a double-sided board. It only goes to 150-380°C (302-716°F). Lead free usually needs a tip that can get upwards of 425°C (800°F). Could be a part of the problem.

Yes, 380°C exceeds the melting or reflow point for lead free. But, when you're sinking that heat (wattage) into the board, the temp obtained at the via just barely makes the solder soft. You risk damaging the board and surrounding components.

Toast

[Pyr0Beast]

Re: iMac G5 stuck component leads

Lead free does not need anywhere near 400 deg C.

You need a good tip and a good soldering iron.

PREHEAT the board to 100 or more deg. C, I recommend 180 deg. C or more.
Then soldering is a piece of cake.

Drilling WILL ruin the pads.

[Toasty]

Re: iMac G5 stuck component leads

For a DEsoldering station it does. Please see my second post, second paragraph.

Again, drilling will ruin the via's, not the pads.

On single sided boards, the higher heat is usually not needed. But, I use it anyway because I have an on board timer that says NOW YOU IDIOT!

Desoldering stations do not have tinned tips. The contact between tip and solder is not "wet" (tinned). The tips are chromed steel and the solder does not stick. It needs to provide a higher heat level than a soldering iron which does make a "wet" connection and a significantly higher level of thermal transference.

If you owned a station of this type you would see the problem.

You still need a high power, high temp iron with a large (high mass) tip to work on these boards as the heavy traces on BOTH sides sink the wattage very effectively.

When using a soldering iron, I typically use a 800°F (425°C), 3/16" (6 mm) chisel tip on its corner. When using my desoldering station (on these boards), it is set to about the 400°C (750°F) mark, and I crank it up a bit more for the 2 b*stards on the double sided ground plane.

Preheating is always a good idea on these double sided boards, but many people do not have the resources or ability to provide that while attempting to get a cap out.

Excessive heating on these PSU's also makes the nearby SMDs likely to fall off. Not a pretty sight. A higher temp concentration in the ways I have described, makes this a much less likely problem.

Cheers!
Toast

[duffling]

Re: iMac G5 stuck component leads

Excellent, thanks for the tips. Will certainly avoid drilling and try to return the desoldering station for a refund

[Toasty]

Re: iMac G5 stuck component leads

Mine:
http://www.circuitspecialists.com/prod.itml/icOid/9750

I recommend extra tips (medium & large), and extra coil filters. Saves later shipping.

Toast

[duffling]

Re: iMac G5 stuck component leads

The blackjack station looks identical to the Aoyue 474, the gun and tips etc are the same.

The actual unit it'self is much different but do these models share the same gun and parts?

[Toasty]

Re: iMac G5 stuck component leads

According to the specs and parts pages, the guns are different:
A = B1002, BJ = B1002A.

There's a difference in the replacement heating element number:
A = C005, BJ = C005A

*If* you believe the specs..., the BlackJack goes to 896°F whereas the Aoyue only goes to 716°F... using the same gun. Both state 70W power consumption and the spec sheet looks identical.

How far up did you have your temp control turned?

Toast

[Pyr0Beast]

Re: iMac G5 stuck component leads

Ah. I see that now.

If you owned a station of this type you would see the problem.
Yes, that's why I avoid desoldering stations completely.

You still need a high power, high temp iron with a large (high mass) tip to work on these boards as the heavy traces on BOTH sides sink the wattage very effectively.
45W seems to work just fine as long as the board is hot otherwise, you can't even melt solder on some.
With 60W (unregulated) it works better, but you also burn the board pretty fast once its temp goes up.

Preheating is always a good idea on these double sided boards, but many people do not have the resources or ability to provide that while attempting to get a cap out. Excessive heating on these PSU's also makes the nearby SMDs likely to fall off. Not a pretty sight. A higher temp concentration in the ways I have described, makes this a much less likely problem.
Yup. Or burn the plastic near it.

I use the ceramic (infrared) heater for preheating. It works excellent and it is flat.
Same way it is done at manufacturer.
Also, you need preheat to solder things back so solder gets nicely sucked into the hole.

[duffling]

Re: iMac G5 stuck component leads

Started at about 80% , then cranked it. Worked fine at about 70% for replacing power supply caps (iMac PSU)

By the way , my Aoyue is a B1002A Gun , it's a 474a+ model. They gave me the 474 at first which was terrible. Gave it back and they gave me this one. Could it be this is an updated 474 with better temps?

I tried the suggestions using standard 60/40 to flow the joint prior to desoldering and it worked like a charm 98% perfect removal.

Had to flow a few of the holes and couple of times when the cap was removed and solder was dragged over the hole but apart from that all went well.

Thanks again.

[Toasty]

Re: iMac G5 stuck component leads

Excellent!

[ratdude747]

Re: iMac G5 stuck component leads

good to hear... ground planes are a b!tch to deal with... my 30w xytronic 258 craps out on ground planes... to cheap to get something heavier... for what i do, it works...

[duffling]

Re: iMac G5 stuck component leads

Yes they certainly are. Still have two component legs stuck will just have to keep trying till they are free but certainly flowing solder first makes it a ton easier , if I had this in the first place it's likely there would be none stuck.