Hard solder

[reeferman]

I’ve been soldering on consumer electronics since 1965 and consider myself very competent, but this Vizeo has me stumped. It was given to me by a friend who got excellent service out of it (since 2013 or so) until it broke. I don’t work on Vizeo, but since this was such a good set I thought I’d try my hand.

I removed and replaced some SMD regulators and fuses, no problem. The problem was trying to remove some bulging electrolytics. I’ve tried heating it (using fresh flux, flowing fresh solder on the joint) with many types of tips at different temperatures, and even used my old Weller that puts out 100+ watts, all to no avail. The solder just sits there. I finally cut off the caps above the board. Even then I couldn’t get the solder to flow. I wound up soldering the replacement caps on the stubs.

If I didn’t know better I’d swear they used an epoxy. Maybe concrete.

Has anyone else experienced this and have a possible solution?

Thanks
Phil

[MadMan]

Possible the PCB pads that the electrolytics were soldered to are just too big and have too big a thermal mass? Clean your solder tips, especially where they connect to the iron for good thermal conductivity. Or electrical conductivity for a solder gun. Can't tell you how many times I get frustrated with an iron or gun that seems smoking hot, but just isn't enough to melt anything.

Also remember modern solder is lead free and has a higher melting temp. For all we know, they used something even tougher to hold the larger components, like electrolytics. Could be like nickel based solder. No idea why though. I mean, it would make some sense to have more mechanical holding power for large components, but seems like an unnecessary extra expense of material and labor for what's still sort of a run-of-the-mill PCB.

[reeferman]

Thanks for the reply.
The thru holes are small as the caps are 220 @16 and 25 volts.
I cleaned the tips so many times I could almost see myself and mechanically speaking everything on the solder station and Weller were tight.
I guess I'll just write this off as one of those things that can't bee logically explained.

I replaced some electrolytics on a Samsung tonight. So simple it was like turning a light switch on and off.

[MIPS]

Two issues.
One as mentioned these boards have some pretty crazy thermal mass so most irons you would competently repair them with are not powerful enough or will not stay above the melting point long enough to melt the joint.

The other is lead-free solder requires significantly higher temperatures to work with.
When I recap modern motherboards I'm forced to use a Weller ETDD tip with the station cranked to max. It's really hard on the tools and tips.

[jhalphen]

Hi to all,

I experienced the same problem a few years ago when RoHs became mandatory.
did some research & found an explanation.

Essentially, have two complete separate sets of soldering/desoldering tools.
One for RoHs, one for traditional rosin-core work.

The explanation given was that even minute quantity mixing of the two types of solder gives what was called "an eutectic mix of metals" and was found to not even melt well at 515°Celsius (guaranteed destruction of PCB traces).

Even just a "wetted" soldering iron tip is enough to provoke the problem.

The chap who wrote the article solved it this way :
- on RohS soldered circuits, used RoHs iron to desolder.
- cleaned component pads/holes extremely thoroughly
- mounted new components using rosin-core with other iron

I experienced exactly the same problem as ReeferMan while trying to replace 6 x through-hole electrolytics on a vintage NetGear DSL modem.
All i got was clobs of un-meltable mixed solder lumps, whatever the tip temperature. Did some searching to understand why.

i hate RoHs ! lumpy/grainy aspects & heightened long term risks of bad contacts.

Best Regards
jhalphen

[zeno]

Another reason I quit 8 yrs ago after 40+ yrs in the biz.

73 Zeno
LFOD !

[reeferman]

Hey guys,
Thanks for the replies.
I figured there must have been a change in the solder.
From now on at the first sign of rock hard solder, either I pitch the set or snip snip like I did this one (which BTW gives a very nice picture for a Vizeo).
Phil