Soldering Lesson Learned Again

[Tom Bender]

Years ago I could not get a copper pipe joint to take solder. 5 tries and it still leaked, Aarrrgh! Turned out the liquid flux was old. New paste flux and presto!

But that was plumbing. Today I had to solder the electrical connections on LED strip lights. I had never done much electrical but believed that the old rosin core solder would work. After much frustration I decided to put on a dab of paste flux and presto!

[Jim Koepke]

Years ago I could not get a copper pipe joint to take solder. 5 tries and it still leaked, Aarrrgh! Turned out the liquid flux was old. New paste flux and presto!

But that was plumbing. Today I had to solder the electrical connections on LED strip lights. I had never done much electrical but believed that the old rosin core solder would work. After much frustration I decided to put on a dab of paste flux and presto!

Even if it still looks shiny metals can oxidize causing solder not to take hold. Different types of rosin core solder use different fluxes. Some deteriorate more over time than others.

There are also different types of flux for the different types of material that may be soldered.

To top it off many solders no longer contain lead.

My last time soldering was also years ago.

jtk

[Paul F Franklin]

One word of warning...many plumbing fluxes are corrosive if not removed. If that's the flux you used, you should remove the residue. Most can be removed with hot water or alcohol. Neither will hurt the LED strip, just make sure power is removed and you let it dry before applying power.

[John K Jordan]

I second the warning about the type of flux. I don't know what's in today's paste flux but in the past a plumber's flux could be a real problem with electronics. One problem is the heated flux might flow into places where it might be difficult or impossible to remove.

I always use the rosin core but have never had a problem with old solder, even with solder that is 40 years old. Part of the soldering equation is the soldering iron - I always use professional temperature-controlled soldering stations. Too much heat or not enough can both be a problem with circuit boards and components. A big factor in the heat is the mass of the two parts to be joined - the higher heat sink of heavier/thicker components requires a lot more heat than thin traces on circuit boards and the coordinated timing of the iron and touch with the solder can be critical.

Pre tinning all connections can really help, especially with wires. A lot of practice helps the most but that's hard to come by quickly!! :) (I started with circuit design, construction, and repair in the '70s and have put in some time - each memory board on my first computer had 1440 solder connections. Yikes, I don't know if my hands would tolerate even one of those boards today!)

With limited experience I recommend making at least a half dozen or so similar practice connections before starting on real connections.

JKJ

[Tom M King]

You can buy rosin flux too. You can probably even get a small container off ebay, with free shipping.

[mike stenson]

You can buy rosin flux too. You can probably even get a small container off ebay, with free shipping.

A 2oz jar is less than $10 and will last a very long time... I store mine in the fridge in the shop (otherwise it just melts anyway).

[Bill Yacey]

A lump of violin rosin is all you need; also known as colophony, this is what is used in rosin core solder. Newer lead free solders have a much higher melting temperature and can be difficult to re-flow. It's important to use the right solder too; for electronic work, 60/40 lead/tin solder is the correct solder to use; don't use plumbing solder.

Please don't ever use any kind of acid paste for soldering electronic connections. It's nigh impossible to remove all the acid residue, and will eventually corrode and destroy the connection.

[John K Jordan]

A 2oz jar is less than $10 and will last a very long time... I store mine in the fridge in the shop (otherwise it just melts anyway).

The best flux I ever used for electronic components came in a liquid form. One tiny drop from an applicator with a fine stainless steel tube was enough to solder almost anything.

For those soldering a lot of electronic components, something I find very helpful is ultra-fine rosin core solder. What I have is less than 1/4 the diameter of most solder available in retail outlets. I use it more than any other as it can make a cleaner and quicker connection than "fat" solder, often with less heat.

For anyone looking for a better soldering iron, this is one of the soldering stations I use. https://www.amazon.com/gp/product/B000BRC2XU There is a new model with a digital temperature display but I haven't tried it. I also have two of the older Weller units that control the heat automatically with the tip - for a hotter iron insert a hotter tip. I use one just for repairing plastic parts.

JKJ

[mike stenson]

The best flux I ever used for electronic components came in a liquid form. One tiny drop from an applicator with a fine stainless steel tube was enough to solder almost anything.

For those soldering a lot of electronic components, something I find very helpful is ultra-fine rosin core solder. What I have is less than 1/4 the diameter of most solder available in retail outlets. I use it more than any other as it can make a cleaner and quicker connection than "fat" solder, often with less heat.

For anyone looking for a better soldering iron, this is one of the soldering stations I use. https://www.amazon.com/gp/product/B000BRC2XU There is a new model with a digital temperature display but I haven't tried it. I also have two of the older Weller units that control the heat automatically with the tip - for a hotter iron insert a hotter tip. I use one just for repairing plastic parts.

JKJ

Sure, but the paste isn't designed to be liquid ;) So it just spills out of the tin, and it's hard to apply that way as well

I've given up on Weller in recent years as they seem to be hit and miss, and generally just recommend (and buy) Hakko.

[Jim Koepke]

It's important to use the right solder too; for electronic work, 60/40 lead/tin solder is the correct solder to use; don't use plumbing solder.

The preference of many electronics technicians is actually for a 63/37% lead/tin solder for its eutectic properties:


63/37 solder is made of 63% tin and 37% lead. It has a melting point of 183°C, slightly lower than the more common 60/40 blend. The primary advantage of this solder is not the lower melting point, but its eutectic property. Non-eutectic solders, like the 60/40 solder, have a semi-solid state between solid and liquid. If a joint is moved during this stage, it can result in what is called a cold solder joint. Eutectic solders, like the 63/37, do not have this semi-solid state and are thus considered easier to work with as it produces fewer bad joints. However, these solders typically cost more than their non-eutectic counterparts.

If you are working on a circuit board with a back up battery, it may be a good idea to remove the battery if a lot of soldering is going to be done. This is especially true if using water removable flux. The people in QC thought my brain was scrambled when trying to explain dendrites to them… Until an article on the subject of some metals self plating on circuit boards from HP Labs explained my point. That was before the internet.

jtk

[Paul F Franklin]

Actually, almost all electronics work now is done with lead free solder and water soluble flux. The EU banned lead in consumer products in 2005 or 2006, and that led eventually to widespread elimination of lead in electronics to avoid having to have multiple manufacturing processes. I was still working in the electronics manufacturing industry when the transition occurred and it brought a lot of challenges. Now days, the products and processes are pretty dialed in. I do have some tin/lead solder for working on older electronics gear, but mostly use lead free now for electronics.

[Jim Koepke]

Actually, almost all electronics work now is done with lead free solder and water soluble flux. The EU banned lead in consumer products in 2005 or 2006, and that led eventually to widespread elimination of lead in electronics to avoid having to have multiple manufacturing processes. I was still working in the electronics manufacturing industry when the transition occurred and it brought a lot of challenges. Now days, the products and processes are pretty dialed in. I do have some tin/lead solder for working on older electronics gear, but mostly use lead free now for electronics.

Mea culpa! Most of my soldering work was done before the turn of the century. Very little soldering in this century.

There are still about 5 pounds of old tin/lead solder out in my shop.

jtk

[mike stenson]

Really, it just means you need to have some of both on hand for any electronics repair. For things like soldering wiring harnesses for car stereos, I just still use lead based. It's easier to deal with, and it does better in high vibration environments anyway.

[Bill Yacey]

For PCB work I use lead tin even when lead free solder was used. The lead tin solder still makes a better solder joint.

The melting temperature difference between 60/40 and 63/37 isn't enough to get excited over. We regarded the Ersin 63/37 as more of a boutique "frou frou" solder. Liquid rosin flux can be easily made by dissolving violin rosin in ethyl or isopropyl alcohol.

Years ago, I had a Weller soldering station with the interchangeable temperature controlled tips, a WTCPT if I recall correctly. When that crapped out for the third time in 30 years, I bought one of the newer Weller stations with a dial control for temperature; I like this iron as it has a slimmer barrel, and a selection of about 3 tips works for just about everything: A 1/4" chisel tip for heavy soldering jobs, the stock conical tip that they supply with the iron, and a slim pencil point for SMD work.