Re: gEDA-user: RoHS compliant fab & assy drawing notes

[joeft <joeft@xxxxxxxxxxxxx>]

I have found similar info as what Steve has noted.  Many vendors are letting their parts automatically "roll over" to lead free compliant versions.  This means that if you manufacture something now (during the transition) you will have a mix 
of RoHS and non-RoHS compliant parts.  Some will solder better than others depending on your assembly shop's process.  And you might find this leads to extra documentation overhead should someone want to know what your compliance status is down the road.

Lead free solders will be mostly tin with a small amount of other metals (usually bot not always silver), and they will indeed require higher soldering temperatures.

Board materials and plating will have to change if you were using HAL, as Steve points out.  Many shops will not have gold available as a plating option however and will use matte tin instead.  This brings into play the "tin whisker" problem which it seems not everyone has solved yet.  Gold does not always solder as well as you might like since it can actually diffuse out into your solder.  Unless your shop uses some really bizarre fire-retardant, the plating should be the only board material problem.

One note on part compatibility - watch out if your are using certain plastic packaged ICs (QFP, QFN, some BGAs).  The higher solder temperature profiles can exacerbate problems with moisture.  Some parts manufacturers already require a "bake out" for certain parts.  When you go to the higher solder temps required for lead-free soldering, the "moisture sensitivity level" can increase by two levels (usually from MSL 2 to MSL 4).  This means your pre-loading handling, moisture exposure, and bake out may have to be changed.  Be sure to ask whoever places and solders your parts how they deal with this issue.

I regards to what you need to put on the drawings - I suggest contacting your vendor(s) and ask them exactly what wording to use to get the process you want.  And then make sure they label the finished boards with date codes, UL file numbers etc. so there is some traceability or record of what they did.

Joe

-----Original Message-----
From: Steve Meier <smeier@xxxxxxxxxxxxxxxxxxx>
Sent: Nov 30, 2005 8:40 AM
To: geda-user@xxxxxxxx
Subject: Re: gEDA-user: RoHS compliant fab & assy drawing notes

This is a fine forum for these kinds of questions.

see the web site leadfree.ipc.org


I believe FR4 is complient.

The next issue is surface finish. So HALS is out.. Hot Air Level Solder.

Talk to your vendor but mine recomended a IS410 (gold surface finsh).

Then I presume all your components will be complient (check the data
sheets and pick the proper part numbers). Watch out some manufacturors
are not changing part numbers but rather saying that parts after a
certain date code will be complient.

Lead Tin solder is out. Some sort of Silver Tin is in (i think) higher
temperatures are involved.



Steve Meier




On Wed, 2005-11-30 at 10:51 -0500, Stuart Brorson wrote:
> I don't know that this is the best forum to ask this question, but
> it's a good starting place since we have a lot of knowledgable people
> on this list.
> 
> I need to do some RoHS-compliant boards.  Therefore, I need to create
> fab and assy drawings with the appropriate notes on them calling out
> the correct RoHS-compliant fabrication and manufacturing documents,
> standards, procedures, and materials.  I don't have any experience
> with this.  Does anybody here have an example set of fab and assy
> drawing templates with the correct notes on them?  Or is there a place
> on the web to look at the appropriate boilerplate?
> 
> Thanks,
> 
> Stuart