Does it have to be gold?

[Frank Bemelman]

LCD/PCB with zebra strips always have gold plated pads on the PCB,
at least that's what I've always seen.

I was thinking if it were okay to use simple tinned pads. Looking
for some guidelines, I found this:

http://www.fujipoly.com/design/genDesignGuidelineArticle.asp?ContentItemID=dga_1007

They say:
c.) Contact pad material on the PC board, as well as the LCD, should be
smooth
and regular with thickness tolerances established.

Is that the key issue, a smooth surface? They don't specifically mention
gold plated.

Anyone tried tinned pads before?

 

[Ban]

LCD/PCB with zebra strips always have gold plated pads on the PCB,
at least that's what I've always seen.

I was thinking if it were okay to use simple tinned pads. Looking
for some guidelines, I found this:

http://www.fujipoly.com/design/genDesignGuidelineArticle.asp?ContentItemID=dga_1007

They say:
c.) Contact pad material on the PC board, as well as the LCD, should
be
smooth
and regular with thickness tolerances established.

Is that the key issue, a smooth surface? They don't specifically
mention
gold plated.

Anyone tried tinned pads before?

Frank,
the usual tinning process cannot guarantee a smooth surface. I have been
making boards for PGA-casings and these require a gold finish, the tin is
too uneven.

ciao Ban

 

[Mario Trams]

LCD/PCB with zebra strips always have gold plated pads on the PCB,
at least that's what I've always seen.

I was thinking if it were okay to use simple tinned pads. Looking
for some guidelines, I found this:

http://www.fujipoly.com/design/genDesignGuidelineArticle.asp?ContentItemID=dga_1007

They say:
c.) Contact pad material on the PC board, as well as the LCD, should be
smooth
and regular with thickness tolerances established.

Is that the key issue, a smooth surface? They don't specifically mention
gold plated.

I don't know whether you once disassembled and reassembled things like
digital watches, calculators, digital thermometers etc.

My experience when I did this, is that these things are quite
difficult to get working back again without any problems.
Obviously (and as Ban said) you need a very good finish for
proper contect between PCB and this "magic" rubber. And
even in this case everything has to be perfectly mated.

Regards,
Mario

 

[Spehro Pefhany]

LCD/PCB with zebra strips always have gold plated pads on the PCB,
at least that's what I've always seen.

Carbon coating or nickel is also used.

Here's what one manufacturer suggests (but that gold thickness sounds
pretty generous to me)

---
PCB Coatings
The best material to use for the contact area is gold.
Alternatives are carbon, tin-lead or nickel.
Gold: 50 millionths over 50 millionths nickel
Nickel: 100 millionths
Carbon: 0.001 carbon over copper

 

[Frank Bemelman]

Carbon coating or nickel is also used.

Here's what one manufacturer suggests (but that gold thickness sounds
pretty generous to me)

---
PCB Coatings
The best material to use for the contact area is gold.
Alternatives are carbon, tin-lead or nickel.
Gold: 50 millionths over 50 millionths nickel
Nickel: 100 millionths
Carbon: 0.001 carbon over copper
---

Thanks, luckily they don't advise *against* tinned pads. My favorite
prototype service doesn't provide gold plated contacts. I figure
I can get away with tinned pads, perhaps give it a swipe first,
with that eh, solder-sucking-litze.

I was also thinking about gold plating them myself, with some
cheap $69 kit, but I would have to remove the soldermask, which
isn't very easy to do...

It's all for an ambitious hobby project, for which I want to
use low cost graphic lcd as used in Nokia phones. These are
easy to get and don't cost much. See Ebay #3352101054. There's
a little zebra connector on the back, 9 pads of reasonable
size. The control is easy, not much more than +v and serial
clock and data.

 

[George R. Gonzalez]

LCD/PCB with zebra strips always have gold plated pads on the PCB,
at least that's what I've always seen.

I just opened up my $49 cordless phone, the big caller-id LCD display of
which has lost most of its segments,
slowly, during the two years we've had it, making it hard to tell who's
calling.

I peeled off the carbon zebra flexy pc board, and noticed the pads on the PC
side were tin plated.
The glue used was really strong, but apparently not good enough to sustain
contact for several years.

Soo if you believe this data point, tin plating will work, for about a year,
then gradually decay,
leading to much cussing.


Regards,


George

 

[Spehro Pefhany]

I just opened up my $49 cordless phone, the big caller-id LCD display of
which has lost most of its segments,
slowly, during the two years we've had it, making it hard to tell who's
calling.

I peeled off the carbon zebra flexy pc board, and noticed the pads on the PC
side were tin plated.
The glue used was really strong, but apparently not good enough to sustain
contact for several years.

They don't use any glue. The stickiness was just from the rubber.

Best regards,
Spehro Pefhany

 

[Tilmann Reh]

They don't use any glue. The stickiness was just from the rubber.

They do. It's a hot-melt technology, and I also made experiences
that this is not too reliable...

--
Dipl.-Ing. Tilmann Reh
Autometer GmbH Siegen - Elektronik nach Maß.
http://www.autometer.de

==================================================================
In a world without walls and fences, who needs Windows and Gates ?
(Sun Microsystems)

 

[Tilmann Reh]

Thanks, luckily they don't advise *against* tinned pads.

They do, at least some of them.
I also checked this detail some time ago, and talked to many
LCD module makers. Most of them didn't know anything more
detailed ("we get them completely assembled from taiwan,
and we don't know why they always use gold").
One of them, however, told me that the tinned finish is
subject to creeping surface corrosion from the open sides,
which produces a long-term reliability problem.

So, the known-good materials are only gold, carbon, and nickel,
as mentioned before.

--
Dipl.-Ing. Tilmann Reh
Autometer GmbH Siegen - Elektronik nach Maß.
http://www.autometer.de

==================================================================
In a world without walls and fences, who needs Windows and Gates ?
(Sun Microsystems)

 

[Phil Hobbs]

I peeled off the carbon zebra flexy pc board, and noticed the pads on the PC
side were tin plated.
The glue used was really strong, but apparently not good enough to sustain
contact for several years.

Soo if you believe this data point, tin plating will work, for about a year,
then gradually decay,
leading to much cussing.

Right. Elastomeric connectors don't produce gas-tight connections, the
way that self-wiping metal connectors or wire wraps do. That means that
base-metal contacts will corrode eventually. For prototype use, tin
ought to be fine.

It will also depend on which style of Zebra connectors you're using--the
ones with the metal wires will probably work better with tin than the
silver- or carbon-loaded ones.

Cheers,

Phil Hobbs

 

[Spehro Pefhany]

They do. It's a hot-melt technology, and I also made experiences
that this is not too reliable...

Okay, you mean the heat-sealed flexible connectors. That's not called
"zebra".


Best regards,
Spehro Pefhany

 

[Tilmann Reh]

Okay, you mean the heat-sealed flexible connectors. That's not called
"zebra".

Right - maybe I misinterpreted his sentence, maybe you wrongly focused
on "zebra"...

From his "carbon zebra flexy pc board", I assumed he was reffering
to a flexible foil with zebra-like carbon traces, and that fits the
hot-seal technology.

--
Dipl.-Ing. Tilmann Reh
Autometer GmbH Siegen - Elektronik nach Maß.
http://www.autometer.de

==================================================================
In a world without walls and fences, who needs Windows and Gates ?
(Sun Microsystems)

 

[SioL]

So, the known-good materials are only gold, carbon, and nickel,
as mentioned before.

I wonder if carbon would work for PCI bus connector on the PCB?
Anyone have experience with that? Gold costs too much in small prod. runs.

Siol

 

[Frank Bemelman]

I wonder if carbon would work for PCI bus connector on the PCB?
Anyone have experience with that? Gold costs too much in small prod. runs.

What do/did you pay for the gold plating? What quantities?

 

[SioL]

What do/did you pay for the gold plating? What quantities?

100 - 200 boards.

A quote I got about 6 months ago was about a double (total for a PCB)
for gold plated edge connector.

Siol

 

[Frank Bemelman]

100 - 200 boards.

A quote I got about 6 months ago was about a double (total for a PCB)
for gold plated edge connector.

Double??? Good grief... I'll think I'll order that DIY gold plating
kit and start a business

 

[Zak]

It's all for an ambitious hobby project, for which I want to
use low cost graphic lcd as used in Nokia phones. These are
easy to get and don't cost much. See Ebay #3352101054. There's
a little zebra connector on the back, 9 pads of reasonable
size. The control is easy, not much more than +v and serial
clock and data.

I've seen phone displays with a flex strip connection as well, but I
have no idea about the control of those. I think the flex can be soldered.


Thomas

 

[SioL]

Double??? Good grief... I'll think I'll order that DIY gold plating
kit and start a business

Exactly, ridiculous prices.

In fact that kit might be a cheap way to go I wonder how effective
that KIT thing really is?

Siol

 

[Semih Hazar]

It's all for an ambitious hobby project, for which I want to

use low cost graphic lcd as used in Nokia phones. These are
easy to get and don't cost much. See Ebay #3352101054. There's
a little zebra connector on the back, 9 pads of reasonable
size. The control is easy, not much more than +v and serial
clock and data.

there are LCD modules with metal contacts which are easier to deal with.
(exactly same display but different contact type)

See www.jelu.se / shop / misc parts / PART-NOKIALCD
and also http://www.myplace.nu/mp3/nokialcd.htm


Hope that helps,

Semih

 

[Frank Bemelman]

there are LCD modules with metal contacts which are easier to deal with.
(exactly same display but different contact type)

See www.jelu.se / shop / misc parts / PART-NOKIALCD
and also http://www.myplace.nu/mp3/nokialcd.htm


Hope that helps,

Thanks, I've seen them. These are removed from original
nokia 3310 replacements, have a contact block of goldplated
contacts. Originally it all sits in a plastic frame with
a keypad. The contact block is a loose part, and has to
be glued on. Then you need to make a new bezel or frame to
mount it. Doable, but not very practical. The 5110 just
snaps on, provided you have a PCB with the proper pads
and slots.