Homebrew PCBs

I've just had a double-sided prototype made by PCB Train using their 
low-cost Express prototype service (no solder mask or silk) - I got the 
board in three days for 30 GBP. They use immersion silver for all their 
PCBs, which is new to me. It seems just as easy to solder as HASL tinning. 
It might be a useful alternative to immersion tinning for homebrew PCBs, 
with much better solderability. I don't know how easy it is to use, though.

PCB Train is here, if anyone else is interested in this service:

http://www.pcbtrain.co.uk/welcome.php

They actually make the boards in 24 hours. They don't do any checking of the 
Gerbers for this service, so you need to make sure that the design conforms 
to their specifications.

I'm very pleased with the board. It's nearly all surface mount with an 
Altera MAX II CPLD in a TQFP-100 package. I've assembled enough of it to 
check that I can program the CPLD via the JTAG connector with my USB Blaster 
and it's OK so far. I haven't even got any decoupling capacitors or JTAG 
pullup/pulldown resistors on it yet, so I was a bit surprised that I could 
program it.

Leon
--
Leon Heller
Amateur radio call-sign  G1HSM
Yaesu FT-817ND transceiver
Suzuki SV1000S motorcycle
leon355@...
http://www.geocities.com/leon_heller

Hi Lean,

Immersion silver works great if you use it fairly quickly. However if
the boards stand for more than a month or so, the silver oxidises and
they become quite difficult to solder.

Les

Leon wrote:

> I've just had a double-sided prototype made by PCB Train using their 
> low-cost Express prototype service (no solder mask or silk) - I got the 
> board in three days for 30 GBP. They use immersion silver for all their 
> PCBs, which is new to me. It seems just as easy to solder as HASL tinning. 
> It might be a useful alternative to immersion tinning for homebrew PCBs, 
> with much better solderability. I don't know how easy it is to use, though.
>
> PCB Train is here, if anyone else is interested in this service:
>
> http://www.pcbtrain.co.uk/welcome.php
>
> They actually make the boards in 24 hours. They don't do any checking of the 
> Gerbers for this service, so you need to make sure that the design conforms 
> to their specifications.
>
> I'm very pleased with the board. It's nearly all surface mount with an 
> Altera MAX II CPLD in a TQFP-100 package. I've assembled enough of it to 
> check that I can program the CPLD via the JTAG connector with my USB Blaster 
> and it's OK so far. I haven't even got any decoupling capacitors or JTAG 
> pullup/pulldown resistors on it yet, so I was a bit surprised that I could 
> program it.
>
> Leon
> --
>

Leon wrote:
> ...
> PCB Train is here, if anyone else is interested in this service:
> 
> http://www.pcbtrain.co.uk/welcome.php
> 
> They actually make the boards in 24 hours. They don't do any checking of the 
> Gerbers for this service, so you need to make sure that the design conforms 
> to their specifications.
> 
> I'm very pleased with the board. It's nearly all surface mount with an 
> Altera MAX II CPLD in a TQFP-100 package. I've assembled enough of it to 
> check that I can program the CPLD via the JTAG connector with my USB Blaster 
> and it's OK so far. I haven't even got any decoupling capacitors or JTAG 
> pullup/pulldown resistors on it yet, so I was a bit surprised that I could 
> program it.
> 

I don't know anything about immersion silver. I was surprised Google 
didn't show up much. http://www.freepatentsonline.com/EP1391536.html
mentions a preferable silver immersion solution contains 0.2 to 5g 
silver nitrate with some acid. I'd try citric acid as a start, but my 
AgNO3 is packed away so I can't easy test it. AgNO3 is available from 
any photographic supplier store. Its not cheap. Alternate is buy some 
silver and dissolve it in concentrated nitric acid. But nitric acid 
isn't always easy too get.

Its good to see other low runs PCB companies competing with some of the 
cheap manufactures in Asia. It might mean we expect to see prototype 
PCBs keep dropping in price as the companies improve their process 
efficiency.
The nature of PTH PCBs fabrication doesn't make it easy for anyone to 
cut corners.

On Fri, 28 Mar 2008, Leslie Newell wrote:

> Immersion silver works great if you use it fairly quickly. However if
> the boards stand for more than a month or so, the silver oxidises and
> they become quite difficult to solder.

Incidentally, I'm just about to (once I've thoroughly checked the PCB
layout for correctness!) send off a 4 layer PCB to PCB Train. How does
immersion silver hold up on edge connectors? I think it's the only plating
they offer for 4 layer boards.

----- Original Message ----- 

From: "Dylan Smith" <dyls@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Saturday, March 29, 2008 12:07 PM
Subject: Re: [Homebrew_PCBs] Immersion silver


> On Fri, 28 Mar 2008, Leslie Newell wrote:
>
>> Immersion silver works great if you use it fairly quickly. However if
>> the boards stand for more than a month or so, the silver oxidises and
>> they become quite difficult to solder.
>
> Incidentally, I'm just about to (once I've thoroughly checked the PCB
> layout for correctness!) send off a 4 layer PCB to PCB Train. How does
> immersion silver hold up on edge connectors? I think it's the only plating
> they offer for 4 layer boards.

I think it's only 1 micron thick, so it'll get scraped off quickly. You 
really need gold plating on them, or use an indirect connector.

Leon
--
Leon Heller
Amateur radio call-sign G1HSM
Yaesu FT-817ND and FT-857D transceivers
Suzuki SV1000S motorcycle
leon355@...
http://www.geocities.com/leon_heller

Quoth Dylan Smith at 2008-03-29 21:37...
> Incidentally, I'm just about to (once I've thoroughly checked the PCB
> layout for correctness!) send off a 4 layer PCB to PCB Train. How does
> immersion silver hold up on edge connectors? I think it's the only plating
> they offer for 4 layer boards.

Dylan (and others interested in immersion silver) - have a look at this:

<http://www.pcbfast.com.au/wp-content/uploads/2007/02/surface_finish.pdf>

Gives the pros and cons of the varying finishes that this board house 
offers - including immersion silver.  (And no, it's no good for edge 
connectors.)

Cheers

M


-- 
Matthew Smith
Smiffytech - Technology Consulting & Web Application Development
Business: http://www.smiffytech.com/
Personal: http://www.smiffysplace.com/
LinkedIn: http://www.linkedin.com/in/smiffy