about "computer grade" caps
I have worked in the high-tech industry since the first IBM PC hit the streets in 1984. Some of that time was as a repair tech, but I have always been the hands-on hardware type. I have worked on all manner of computers, from room filling comercial systems to the cheapest consumer grade PC.
In the beginning, there was no such thing as a "computer grade" cap... a cap was a cap, and computers and related hardware were built like tanks. The computer systems from the 60's and 70's were large and comsumed a lot of power. They required a great deal of "quiet" DC current and this was supplied through some very large canister type capacitors. These caps were built to take a lot of heat, deliver a lot of current, and operate very quietly. They were of the highest quality that could be produced, and became known as "computer grade" caps. This lable is still used today to discribe these large canister type capacitors. Although they are rarely used in computers today, they have found use in some very high-end commercial electronics.... Power supplies, radiology, detection systems, etc. They are still very high quaility caps and the cost reflects this ($20 - $300 each).
The quality issues related to capacitors started back in the late 90's. Beginng in the early 80's "mass marketing" concepts began to take hold. The electronic age was just gettting started and electronic devices fit into the mass marketing concepts well. By the 90's the "consumer electronics" machine was in full swing and driving costs down was central to this theme. This resulted in componet manufactures finding ways to make components (including capacitors) in the cheapest possible ways. The marketing pressures to lower costs left the door open for some not-so-honest companies to produce some very bad capacitors (some used stolen information, and you can read about this on the web at http://en.wikipedia.org.wiki/Capacitor_Plague). But regardless of who was selling and who was buying, there emerged a market for cheap capacitors. This set the stage for some real quality issues. Enter the late 90's... where PC's and other electorics, fell into this inevitable circumstance.
Consumer products are designed to be desposable and to have a limited life (3 - 5 years) and components for such cost structures exist. However, capacitors had a history of being reliable devices and the dangers of buying the cheapest ones on the market were not apparent. So with this in mind, I don't think any of the computer manufacutres gave a thought as to how long a cheap cap would last, or that the presures to lower costs would result in such un-ethical practices amoung component providers.... until it bit them in the back side. This is a lesson learned by most reputable manufatures now.
I have to tell you... in my experience, the problems with bad caps was amlost entirely contained within consumer grade products. The commercial system did not see the issues of bad caps often. Work stations, commercial computers, and hardware... are built to high standards and the best components were generally used. When a company has mission critical data (payroll, accounting, prodcut designs, etc) riding on a computer, reliability becomes a very serious business. I serviced a lot of comercial systems, and by far, the biggest issues were from machanical ware.... moving parts failed. The other big issue was chip failures (Which can be caused by a list of things that I won't get into here, but suffice it to say that none of which are related to capacitors). The paradigm that drove comercial systems/products was different then that for consumer products. This provided a "cheap" filter that kept the problem parts out, and prevented the "Capacitor Plague" from becoming much of a problem in this market.
Because of the issues seen in the late 90's, some are using the term "computer grade" to describe cheap, low quality capacitors.... to the contrary, most computers today use (and require) a higher quality cap then say... toys, comsumer quality Audio/Video eqipment, appliances, TVs, etc. So the term is a bit misleading. As the speed of computers increased and the electronics shrank to smaller and smaller sizes, the need for components that ran faster and quieter, and to do it in hotter, smaller spaces was required. Capacitors are no exception to this. Capacitors have improved greatly. So don't let this confuse you. You need to read this phrase in context of the discussion. Computer grade cap are generally of a higher quality then the low cost caps used in toys, and entry level comsumer electorincs. The use of the term "computer grade" as used by manufactures and resellers, usually indicates a higher grade cap. These are not the ones designed to satisfy the "cheapest" consumer cost structures.
When buying capacitors, rememeber the lessons taught by the computer manufactures... you get what you pay for!!! Buy the cheapest cap and you may buy junk. Stay with known brands that have been in the buisness of making caps for a while and you will most likely get good quality. Don't buy the cheapest until you have read the specs sheet. Remember, consumer products still only have a life of 3 -5 years and there are componets that are designed for this cost structure. Many spec sheets (but not always) will state "for comsumer electorics" and you can bet that life expectancy was not part of that product's design criteria. However, with that said.... barring mistakes in manufacturing or design, even a cheap cap from a reputable manufacture, will do what it is supposed to do for a number of years, and most likely... many years.
So don't let the term "computer grade" scare you off. Some of the finest qualiy components today were designed specifically for the deamands of computer systems. What you really need to understand is:
1) The specific market the componet was designed for. This can be tricky, but
filter out capacitors amied at toys and entry level electronics.
2) who the manufacturer is. Even though some highly regarded
capacitor manufacutres have had mistakes, they are few and far
between. When you produce millions of capacitors in a single batch,
they know, there is no such thing as a "small" mistake. If bad caps
get out on the market, it's a big deal... the kind that can ruin a manufacutre's
reputation. So, among the reputable manufactures, quality is a big deal.
Stay with the major brands and you will get good quality.