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ICs - when to socket, when to solder?

E

E. Kunze

Jan 1, 1970
0
In PC monitors, I often see the OSD-processor sitting in a
socket, whereas eg the TDA4858 is soldered onto the board.

Unfortunately, the TDA4858 is the usual victim of a device
failure, whereas (knock on wood) I didn't yet meet a defective
OSD-processor. Unsoldering a multipin chip is much more
tedious than just replacing a socketed one, isn't it?

I can't see technical reasons that demand to solder the
TDA4858 onto the board and would very much like to put
the replacement for the next TDA4858 I'll have to take out
into a socket. Any objections?

What would the technical preferences be for soldering a chip
against socketing it? Concernig cost, a socket wouldn't add
more than a few pence for the manufacturer, would it?
Eb
 
J

Joseph Legris

Jan 1, 1970
0
E. Kunze said:
In PC monitors, I often see the OSD-processor sitting in a
socket, whereas eg the TDA4858 is soldered onto the board.

Unfortunately, the TDA4858 is the usual victim of a device
failure, whereas (knock on wood) I didn't yet meet a defective
OSD-processor. Unsoldering a multipin chip is much more
tedious than just replacing a socketed one, isn't it?

I can't see technical reasons that demand to solder the
TDA4858 onto the board and would very much like to put
the replacement for the next TDA4858 I'll have to take out
into a socket. Any objections?

What would the technical preferences be for soldering a chip
against socketing it? Concernig cost, a socket wouldn't add
more than a few pence for the manufacturer, would it?
Eb

Sockets are more prone to failure, just like any other any
electromechanical device, but the difference may be insignificant unless
you have unusual vibration, dust, corrosion, etc.

Manufacturers are concerned about the above, the size of the socket,
protecting the socket during automated soldering and cleaning, the cost
of the socket and also the cost and reliability of inserting the chip
into the socket. In your case it's probably a good idea to add the
socket because you are already spending a lot of time getting inside the
housing and diagnosing the problem.

Removing a soldered chip is easy if you don't mind destroying it. Use
tiny wire snippers to cut every lead close to the body, remove the body
and then remove the pins from the board one-by-one.
 
A

Active8

Jan 1, 1970
0
ebkunze@t- said:
In PC monitors, I often see the OSD-processor sitting in a
socket, whereas eg the TDA4858 is soldered onto the board.

Unfortunately, the TDA4858 is the usual victim of a device
failure, whereas (knock on wood) I didn't yet meet a defective
OSD-processor. Unsoldering a multipin chip is much more
tedious than just replacing a socketed one, isn't it?

you haven't done it yet?

takes longer, but it isn't hard. haven't seen a single pin chip yet,
either.
I can't see technical reasons that demand to solder the
TDA4858 onto the board and would very much like to put
the replacement for the next TDA4858 I'll have to take out
into a socket. Any objections?

not as long as the unsocketed chips don't complain. he may block their
view of the surroundings ;-)

i would have done it by now. i've socketed many defective chips so i
don't have to rework the board over and over. eventually a trace is
going to lift and piss you off.
What would the technical preferences be for soldering a chip
against socketing it? Concernig cost, a socket wouldn't add
more than a few pence for the manufacturer, would it?
Eb

multiply that by the number of units mfg'd and it adds up.

i haven't had to mess with monitors for a long time. i don't know what
these chips are. if the OSD proc is a programmable device, it might be
conviently socketed for firmware upgrades or, more likely, different
models of monitor using the same board.

i don't like sockets in a final product. simple DIP sockets may be
cheap, but i've seen sockets for SMD parts that are pricey. they're nice
for prototyping, but a mfg wouldn't want to pay for 'em. with RF and
high speed digital, i'd be thinking of the strays, but this is an OSD,
so i don't see a prob. again, i don't know what the chip is.i'd go for it.

mike c.
 
S

Spehro Pefhany

Jan 1, 1970
0
In PC monitors, I often see the OSD-processor sitting in a
socket, whereas eg the TDA4858 is soldered onto the board.

Unfortunately, the TDA4858 is the usual victim of a device
failure, whereas (knock on wood) I didn't yet meet a defective
OSD-processor. Unsoldering a multipin chip is much more
tedious than just replacing a socketed one, isn't it?

I can't see technical reasons that demand to solder the
TDA4858 onto the board and would very much like to put
the replacement for the next TDA4858 I'll have to take out
into a socket. Any objections?

What would the technical preferences be for soldering a chip
against socketing it? Concernig cost, a socket wouldn't add
more than a few pence for the manufacturer, would it?

Probably has much more to do with there being firmware in the OSD
processor and wanting to be able to deal with possible changes, delays
or upgrades. I doubt repairability entered into thinking at all (well,
maybe when they decided to screw the case together rather than
permanently ultrasonic-weld it shut). Sockets are very cheap in
quantity, but as with any cost it has to be justified by some saving
in their process.

Best regards,
Spehro Pefhany
 
T

Tim Shoppa

Jan 1, 1970
0
E. Kunze said:
In PC monitors, I often see the OSD-processor sitting in a
socket, whereas eg the TDA4858 is soldered onto the board.

Unfortunately, the TDA4858 is the usual victim of a device
failure, whereas (knock on wood) I didn't yet meet a defective
OSD-processor. Unsoldering a multipin chip is much more
tedious than just replacing a socketed one, isn't it?

I can't see technical reasons that demand to solder the
TDA4858 onto the board and would very much like to put
the replacement for the next TDA4858 I'll have to take out
into a socket. Any objections?

What would the technical preferences be for soldering a chip
against socketing it? Concernig cost, a socket wouldn't add
more than a few pence for the manufacturer, would it?

Adding a socket adds unreliability. You get some choice as to the
level of unreliability by choosing the package and the quality of the
socket, but you are still adding some unreliability by adding the
socket. The inside of a monitor is probably one of the worst places
to have a socketed part (frequent thermal cycling by most users).

As you point out, sometimes the socketed component is less reliable
than the socket. To the manufacturer, the relevant factor is warranty
costs from the unreliability added by a socket vs warranty savings by
making it easier to replace the TDA4858.

The cost of having *any* product returned for service during warranty for
either component or socket failure is
very high. The additional cost savings from having a socketed part
may be real but are probably completely offset by the costs associated
with returns due to unreliable sockets.

Tim.
 
D

Dr._Flouride

Jan 1, 1970
0
Tim Shoppa said:
Adding a socket adds unreliability. You get some choice as to the
level of unreliability by choosing the package and the quality of the
socket, but you are still adding some unreliability by adding the
socket. The inside of a monitor is probably one of the worst places
to have a socketed part (frequent thermal cycling by most users).

As you point out, sometimes the socketed component is less reliable
than the socket. To the manufacturer, the relevant factor is warranty
costs from the unreliability added by a socket vs warranty savings by
making it easier to replace the >
The cost of having *any* product returned for service during warranty for
either component or socket failure is
very high. The additional cost savings from having a socketed part
may be real but are probably completely offset by the costs associated
with returns due to unreliable sockets.

Tim.

When soldering most IC's by hand always use a socket: its harder to burn
them up that way. I looked up the TDA4858 and found it an obsolete part
specificly designed to work around heat and monitors. It is rated to be
soldered for ten seconds at 265 Deg C(477 deg F). According to the spec
sheet it will operate up to 70C or 126F. It is a Geometry Correction System
for Multi-Frequency Display chip, it looks kind of like it was designed to
work around high heat, and therefore manufacturers could save a few cents
per unit (millions in a large scale deal) by not socceting that part. If
you're doing the soldering by hand always use a socket on a multi pin chip,
and yes they are a bitch to desolder.Whille thermal contracting and
expansion might be a factor in using or not using a socket, I'd just buy the
one designed to minimise this problem, I'm sure they make one. Its weird
they would not socket the part that breaks most often. If I knew for the
fact that the soldered chip was bad I would cut all the legs off, manualy
desolder the pins leaving good holes, and solder in a decent quality
socket. Manufacturers usually care a lot less about returns than operating
expense; if your selling a $50 product they usually give you the old "fully
warrented until you break it" kinda deals and expect you to just buy another
one..I suppose a monitor is a higher ticket item though..The real problem is
that we live in a disposable society where the only thing that matters to a
large corp is the bottom line of what it cost us versus what we get to sell
it for. When I'm building by hand I'll socket most IC's and use heat sinks
on transistors and diodes as well as smaller caps and pots.

I'm not above the law... I'm beyond it. -George Carlin
 
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