Component Shelf Life: How To Use All That Old Junk | Hackaday

There are two types of Hackaday readers: those who have collected a lot of parts (in other words, a lot of trash) over the years, and those who will have decades from now on. It's easy to draw a lot of things, especially things you might use in multiple designs. Price breakpoints for quantities of 10 or 100 can be tempting, and since local parts stores have replaced dinosaurs, having personal inventory will definitely speed up the hacking process. However, this is not a perfect solution because certain components do have a shelf life and will degrade in some way over time.

If your storage cabinet contains older electronic components, you may find that their ageing is not good, but it can sometimes be resolved. Let's take a look at the shelf life of common parts, how to extend their lifespan, and what to do if some rejuvenation is needed.

More than 20 years ago, I purchased hundreds of common values ​​for the E24 series of 1/4 W through-hole resistors-169 different values ​​in total. In the past 20 years, I rarely need to buy resistors for rapid prototyping or even small batch circuit boards. Whenever the trash can becomes empty, I restock. Recently, I started to buy various surface mount components, including resistors, capacitors and a few inductors. The fact that I need to stock multiple sizes is offset by the lower unit cost of SMD parts, so the initial investment is roughly the same, and it is convenient to have parts on hand.

Although I have never encountered the problem of soldering through-hole resistors, it proved from the beginning that there was a problem with the SMD parts in the sample manual. I found that some components cannot be reflowed correctly: they float on top of the molten solder, move around and do not stick to the PCB, and in some cases are only held by the flux. This is often referred to as a "pillow" defect. After some experiments, I concluded that some of the component sample books may be filled with cutting tapes from very old component reels, and these tapes are no longer suitable for automatic placement and assembly. I imagine a small cottage industry—somewhere—cut out expired scrolls, stuff them into books, and sell them on eBay.

After being frustrated by having to press the component with tweezers during reflow to make it stick, I turned to

For help. [salec] There suggested that I try to wipe the components on a piece of plain paper to clean them before putting them on the PCB. To my surprise, this works like a charm. The cleaned components are well welded. Later, I looked at some components under a microscope and found that an oxide layer (which can be easily removed with paper techniques) was displayed on the terminals, which prevented the solder from properly wetting them. If you try this operation yourself, please make sure to wash your hands thoroughly afterwards, because these older parts may use tin-lead solder, and very fine particles will be produced during the cleaning process, which are easily absorbed if ingested. At the end of this article, there is a short video showing the process of cleaning these components and the impact on their performance during reflow soldering.

It turns out that solderability is a measurable property. By immersing the component terminals in molten solder and checking the resulting solder film, its soldering performance can be evaluated. One form of this "press and see" approach is

(PDF), which also includes an accelerated aging test, which exposes parts to water vapor at around 90°C. When passing the magnification inspection, the pass/fail criterion is 95% solder coverage.

In the good old days when lead was used to make solder, it was necessary to regularly test the solderability, because the lead-tin alloy is easily oxidized and will affect the solderability. This effect is not so obvious in lead-free solder. Actually,

(PDF) shows that the oxide layer thickness of tin-lead solder is ten times that of tin-copper or tin-silver solder. This is what led me to believe that the problematic SMD components I encountered were old, tin-lead coated parts.

One

(PDF) Explains some discerning customers' age restrictions on current production parts. The U.S. military has lifted the date code restrictions on parts, and NASA now only requires parts to be inspected after 5 years to see if testing is required. Before the advent of lead-free solder, military applications required retesting the solderability of components after three years of date code. More evidence of long shelf life comes from

(PDF), this file has no effect on ICs stored in a humidity control environment for more than 15 years.

Therefore, if you buy RoHS-compliant parts today, they may exist for a long time. On the other hand, if you buy parts from an online auction site of unknown origin, or have accumulated lead solder-coated parts, you may need to solve the solderability problem at some point. For old through-hole components, I often solder them in place before fixing the leads to the prototype with nails and a small amount of fresh solder, as this helps to form a good joint. In theory, this technique can be used with surface mount components, but in practice, it is much more difficult. The tricks on paper are much easier.

Ordinary FR4 printed circuit boards will also age. Although the base material can absorb moisture and in some cases needs to be pre-baked before soldering, for amateurs, the primary consideration is to reduce solderability over time. Like component leads and pads, surface treatment determines how aging will affect the usability of the PCB. Common finishes for hobbyist prototype boards include leaded and lead-free HASL (hot air surface leveling) and ENIG (chemical nickel/immersion gold).

The literature lists the "excellent" shelf life of tin-lead HASL for more than 12 months, while lead-free HASL and ENIG are both listed as 12 months. You might think that the gold plating will maintain solderability indefinitely, but the gold plating is actually a bit porous and allows oxygen to contact the nickel layer, which is easily oxidized. Based on the shelf life of components with similar surface treatment, the shelf life of tin-lead HASL is longer than that of lead-free HASL, which is somewhat surprising, but your mileage will vary depending on storage conditions.

The recommended method for long-term storage of PCBs is vacuum sealing. If you have a kitchen vacuum sealer, you can try it if you want to keep it for a while. If there is a desiccant, throw it in. Moreover, if one day you find that you only use an old PCB that cannot be soldered, you can try to use some additional flux, or even try to quickly dip it in the etching solution (and then rinse it thoroughly) to restore solderability.

Interestingly, if you want to etch your PCB, you may not have to worry about aging at all. I recently discovered a PCB that was etched by toner transfer in February 2000, and then I threw it into a box and forgot. Now, after quickly wiping with a paper towel soaked in acetone, you can find that the clean copper is ready, and it can be soldered under the carbon powder for nearly two years. However, as soon as you remove the toner, the clock will start ticking. If the waiting time is too long, you may need to clean the copper cable again before soldering (Scotch-Brite pads are my tool of choice). This PCB is one of the two PCBs I made for the PIC16F84 LED clock project. The other board is filled and may be nearby.

Rod or wire solid solder contains almost no flux, which is always there. Even if the exterior may be oxidized, apply flux appropriately during the soldering process-if your solder does not come with it, you need to apply flux-the joint will be fine. Although the manufacturer will tell you that the solder wire will eventually deteriorate due to the slight corrosive effect of the flux, even the flux-cored wire seems to have almost unlimited service life. I have used some very old flux-cored wires, but I have never heard that anyone-at least on an amateur level-has a serious problem with old solder. On the other hand, if you are assembling commercial products, you may have to follow the solder manufacturer’s recommendations, although there is less chance of encountering old inventory in this environment.

Solder paste is another matter. It must have gone bad, I have seen it. Depending on the manufacturer and product, there will be an expiration date on the package, and instructions for refrigerated storage are usually provided. The solder paste contains very fine metal balls mixed with liquid flux. Over time, the flux will dissolve the protective oxide layer on the outside of the solder balls and fuse them together. This effectively increases the viscosity of the paste, making it more difficult to use-especially if you use a syringe and hypodermic needle to assemble the prototype. This process also reduces the efficiency of the flux, so during reflow, the ability to dissolve the oxide layer when really needed is small.

In an amateur environment, you can push things a little bit. I have stored a syringe, claiming that it has a shelf life of one year after refrigeration and about three years out of laziness at room temperature. Although it can still "work", it is much easier to use a new syringe of the same material at the end. I won't do it again-I ended up doing a lot of unnecessary rework. There are some solder pastes on the market that do not require refrigeration:

For example, it can be officially stored for one year at room temperature. I'm sure that compared to amateurs, its launch time may be longer. The only drawback is that it seems to only be used in relatively large containers.

Therefore, these are some of the problems that may be encountered when using old parts. If you know anyone else, you can share in the comments below. We all want to know them.

I am not even going to discuss the aging problem of electrolytic capacitors. Between the electrolyte drying out and the oxide layer that may need to be reformed, they are absolutely terrible, but I have to mention it here just in case anyone doesn’t know this, especially since we recently ran

.

At the same time, you can watch a video showing how to clean SMD parts and the results. It’s only 2:20 long, but if you want to jump directly to the good part of showing reflow,

Thank you!

Before placement, I did not realize that SMD components would form a thin and strong corrosion layer.

Generally, most suppliers say that the shelf life of sealed SMD parts spools is 3 years, because even in plastic bags, the spread of moisture can cause problems.

Another phenomenon is that some parts with an accuracy of 0.1% can stabilize to their stable value during this time.

Usually, people find that mixing excess solvent-diluted flux into SAC305 solder paste will solve most problems, such as tombstones. However, once the additional flux is mixed, it usually takes only a few weeks to use the remaining solder paste even after refrigeration. Note that silver solder is very suitable for sticking to dozens of different coatings used by manufacturers.

The sample book is usually exposed to the atmosphere without a desiccant.

Youth car

;)

I just want to say that I am not against fair use, and I am a loyal reader of Hackaday, and I know that Disney is a billionaire company, so it will not be harmed, but as an artist, your use of begging is from Aladdin Jafar, without a signature or permission, sat with me.

That's not Jafar, it's Julian Assange. :-)

The implication that Julian Assange (Julian Assange) is or once has a keen interest in the Arabic artifacts locked in the secret cave is false and slanderous.

My first thought when I saw this article was that I am not an artist.

I want to know why he looks familiar...

I'm pretty sure I worked with that guy in the 70s.

Friends, you are too nervous. I don't think Jafar has an affinity for China's surplus component reel, while the aforementioned unnamed colleagues do not. Welcome to the mixing culture-your negative memes will adapt to our needs.

+1

The culture of freedom is richer

A culture that brings creators into poverty, with endless resources.

Obviously it was not Jafars who changed the self-begging. The poor bastard sold his golden teeth to buy more electronics. The absence of dark circles around the eyes indicates that the manga depicted has received the necessary sleep and that it has not been spent all night troubleshooting some psychiatric equipment, which was cooked in a similar crazy state the previous night. Therefore, it is not Jafar, and obviously unbelievable. The lack of hook nose and inclusion reel and the phenomenon of flying parts are also obvious.

This seems to be a fair objection.

really? Will you receive such comments on hackday?

At least on torrentfreak, you know they are trolls, but here?

At the same time it has also been revised (he did not hold a roll of smd in the movie...)

A very useful article, I am very glad to see you now writing for Hackaday!

I never expected the solder to deteriorate. I'm still using up the solder left by my father. I think he got it from the work he did in the mid-1970s. It still works normally. I only do through-hole soldering.

This is a good point. I think the resin may dry out, but I also think it will take a long time. When I was young, I had to buy solder in small quantities, but then I found some good coil deals. One did fail, but it seemed to have the wrong label or the wrong combination at the time (I don't remember which one). I do have a "big" roll of paper, nice and thin in diameter, which lasted for about 30 years until it was used up. A new volume started about 5 years ago, but it is too thick to keep me alive.

Michael

>>"In the next twenty years"

That’s why I like Hackaday...the new realization of "Decade Counter"...

That might explain my disgust with my old batch of Vero boards, which is almost impossible to solder to...

Have you tried to clean it in any way?

According to the bag, it was still slowly running the 5mm red LEDs from the 2000s and 1980s until their shelf life expired in 1991.

10x10x20 led cube?

Garbage is what you throw away, and garbage is what you leave... I call it inventory.

Thank you! I now have a new term to use extra nonsense with my wife...stock in the garage.

Regarding solder wire: I have been using my father's spool for many years without problems-in fact, it can perfectly solder circuit boards that still have photoresist! On the other hand, I have a lot of trouble with the new spool, even if it is not a cheap one...

Just cure:

For hobbies, you may need to buy separate solder balls and flux for long-term storage and mix them a little before use.

Has anyone tried it?

Great article. Thank you!

My electronic lecturer told us to use the eraser on the #2 pencil to remove the oxidation on the copper track. I haven't used this technique for a while, but I remember it worked the last time I tried it.

Wow!

I want to pay tribute to Ted... This is the only HaD article I have ever read. The author not only watched the linked video, but also told you how long it took and where to jump to the best part!

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