I guess you would have to go back and ask Mother what her guidelines
state. The rest of us go by J-STD-001 or IPC 610.
But I am impressed that you would go to such lengths as to please her,
bless your heart. You are indeed a fine boy. I would be most interested
in the other clauses that Mother lists.
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Timothy McGrady
Sent: Friday, November 24, 2006 6:42 AM
To: [log in to unmask]
Subject: [LF] Low Melting Point over High Melting Point solders
I am not an expert in solder applications, so I thought I'd send this
request to the forum for discussion:
I have one small question to pose:- We are making multi layer ceramic
EMI Filter . We are using HMP solder for making contact with disoidal
capacitor which is under exemption but over it we are doing one dip of
lmp solder . Is it ok to use lmp solder over Hmp solder as mother
guidelines clause no7 suggest any solder will be ok with HMp solder. We
are at crossroads and got stuck up at this point .Pl give us some clear
insight and guidelines over it.
----- Original Message -----
From: "Werner Engelmaier" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, November 22, 2006 5:26 PM
Subject: Re: [LF] SnPb attachment of SAC BGAs
> Hi Gordon,
> As I have said in another e-mail, we need to be specific about what we
> are talking about. what can be done in a lab under controlled
> conditions is not an indication of what is possible in production.
> For a 'reflow' process the time parameter is fixed by the belt speed
> which in turn is fixed by the required through-put.
> Sure, you can solder just above Liquidus, but in order to assure that
> enough heat is delivered, you you need to crank up the peak
> temperature in a 'reflow'
> process.
> For the typical through-put in a reflow oven, you need to reach
> Liquidus
> +20C
> for about 3 to 5 seconds at THE ONE solder joint in the whole assembly
> that heats up the slowest [typically the center-SJ of the largest
> BGA].
> What most people do not realise is it is conduction heat transfer
> through the PCB that heats the center-SJ of any BGA, and it is the
> solder paste that reaches its Liquidus long before the BGA ball.
> Sure, for SnPb solder paste you can make a metallurical contact at
> somewhat lower T's than for SAC-paste, howerver you get very odd
> localized compositions as Dave hillman has demonstrated in his
> experiments that have been published.
> Indeed, the Pb-ban of this EU-RoHS directive has resulted in a big
> mess, and there is no easy way around it.
> Unfortunately, I do not have a company paying my way, otherwise I
> would be there.
>
> Werner
>
> ----------------------------------------------------------------------
> ---------Leadfee Mail List provided as a service by IPC using LISTSERV
> 1.8d To unsubscribe, send a message to [log in to unmask] with following
> text in the BODY (NOT the subject field): SIGNOFF Leadfree To
> temporarily stop/(start) delivery of Leadree for vacation breaks send:
> SET Leadfree NOMAIL/(MAIL)
> Search previous postings at: http://listserv.ipc.org/archives Please
> visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
> for additional information, or contact Keach Sasamori at
> [log in to unmask] or 847-615-7100 ext.2815
> ----------------------------------------------------------------------
> ---------
>
------------------------------------------------------------------------
-------Leadfee Mail List provided as a service by IPC using LISTSERV
1.8d To unsubscribe, send a message to [log in to unmask] with following
text in the BODY (NOT the subject field): SIGNOFF Leadfree To
temporarily stop/(start) delivery of Leadree for vacation breaks send:
SET Leadfree NOMAIL/(MAIL) Search previous postings at:
http://listserv.ipc.org/archives Please visit IPC web site
http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100
ext.2815
------------------------------------------------------------------------
-------
-------------------------------------------------------------------------------Leadfee Mail List provided as a service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Leadfree
To temporarily stop/(start) delivery of Leadree for vacation breaks send: SET Leadfree NOMAIL/(MAIL)
Search previous postings at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-------------------------------------------------------------------------------
|
