[sdiy] advice please -- aging chips and caps

[Czech Martin]

Design houses spend billion of dollars for software in order
to compute the average (not RMS, but absolute value)
line currents in all the chips
metal lines. Assuming 10 million transistors and 
9 or more metal layes this is no trivial task.
One reason for doing this is migration.
Al is very "soft", it migrates early.
Cu is "harder", but the sheets are slimmed down,
so the current density is maybe even higher.

Average current densities and temperature
are the important factors important to predict life time. 
Since the absolute average is high in the supply lines,
these lines have the highest risk to fail.

Of course, at low temperature, or even unpowered,
the metal will not age. 10 years lifetime thus means:
10 years of full blast operation under worst case
conditions.

This is something different then owning a synth for 10 years.
If the synth is on for one hour every day, you only use
it 1/24 of the time.

So , excluding very poor designs (chips or pcbs), the chips
should usually live longer then the owner of the synth.


m.c.

-----Original Message-----
From: Scott Gravenhorst [mailto:music.maker at gte.net]
Sent: Samstag, 9. August 2003 20:34
To: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] advice please -- aging chips and caps


I thought the same thing...

Actually, the URL supplied is rather interesting.  I didn't know
about "metal migration".

Are recently manufactured ICs still subject to this?  If the old
ones only last 15 years (expected life), then what of new ones?
 I'd prefer that they outlast *me*.  This is pertinent for me
because I have a 4000 series fetish.

I'm all ears... er eyes...

Tim Ressel <madhun2001 at yahoo.com> wrote:
>John,
>
>I'd replace all the electrolytics. 
>
>Replace the 4000's??? I've never heard of that. The
>only thing I can think of is if the ICs were stressed
>by ESD hits. I'd leave them until something fails.
>
>--tr
>
>
>--- john mahoney <jmahoney at gate.net> wrote:
>> Having read Scott Rider's article "Things to Know
>> When Repairing Vintage
>> Synthesizers" 
>> (http://www.oldcrows.net/~oldcrow/synth/tips.txt), I
>> am now a
>> little concerned about my Korg Mono/Poly, which has
>> reached adulthood
>> (assuming that synth years = human years).
>> Basically, Scott says to replace
>> all old 4000 series CMOS chips as well as certain
>> types of caps.
>> 
>> My questions for you folks:
>> (1) Many of you have years of experience. Have you
>> seen signs of CMOS
>> senility or caps with Alzheimer's?
>> (2) Should I replace the "at risk" components now,
>> even though the synth is
>> working perfectly? Or, wait and see, but *if*
>> something goes bad then
>> replace everything as he suggests. I'd like to add a
>> few extra
>> inputs/outputs/patchpoints to the Korg, so I have
>> reason to do surgery.
>> (See? This is a DIY question!)
>> (3) Given the parts list below, do you see any parts
>> that I should try to
>> obtain now, just in case? For example, if the SSM
>> chips are available,
>> should I stock some? (I don't even know if the SSM
>> chips are available
>> anymore!)
>> (4) Oh, yeah: What's the difference between the
>> HD14000 series and the
>> normal 4000 series, if any?
>> 
>> ICs in the Mono/Poly (thanks to the excellent Zen
>> Mono/Poly website):
>>     SSM2044 4-pole voltage controlled filter
>>     SSM2033 Voltage controlled oscillator (Qty: 4)
>>     MM5837 Digital noise source
>>     Intel 8049 8mhz CPU
>>     HD14007UBP Dual complementary pair + inverter
>>     HD14013BP Dual D flip-flop
>>     HD14042BP Quad latch
>>     HD14066BP Analog CMOS switch
>>     HD14069UBP Hex inverter
>>     HD14071 Quad "or" gate
>>     HD14174BP Hex flip-flop
>>     MC14504 Hex level shifter
>>     NJM4556 Dual high-current op-amp
>>     NJM4558DV Dual op-amp
>>     M5230L Variable output voltage regulator
>>     TL072 Dual J-FET operational amplifier
>> 
>> Thanks to everyone for any and all insight you can
>> offer.
>> --
>> john
>> 
>
>
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-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
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