Hi Phil, thank you for this valuable input. Very familiar with thermal 
relives I will for sure check into this to see if there are any . Could very 
well be that the design was not done to IPC-2222, problem is just how old 
these are. These are an old projects for General Dynamics through a CM not 
to 55110 . These boards are built to IPC6012 class 2. What I am being told 
is that they have never had to pre heat these part numbers before, I am a 
newer vendor so any and all assembly issues just have to be on my side this 
is an old fight that I have fought for years it is up to me to prove that 
the issue is not the PCB they then go from there, normal stuff. What I 
suspect is that the previous vendor did not build to the print and used 1 OZ 
foiled material. If the board was fabricated to the print then there is a 
minimum of 14 oz's of copper overall if not 4-5 lot of difference.
I am squeezing the proper people for an old board so I can get a cross 
section done. If the section does come back and indeed does have the proper 
material that is called out on the print then I'll be in a good cat fight !!
 Thank you and also I would like to thank all the guys on this forum I have 
been on this for years and have always valued it greatly good stuff !!

Bill Dworak




----- Original Message ----- 
From: "Phil Nutting" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, January 26, 2007 5:29 AM
Subject: Re: [TN] Assemble question


Bill,

The boards you describe are very similar to many of our boards.  If this
is an old design board it may be missing thermal reliefs (looks like a
wagon wheel) on each hole that is connected to large copper areas such
as ground or voltage planes.  Without the thermal reliefs the copper
acts like a huge heat sink.  With the thermal reliefs you get thermal
isolation from the large copper mass while maintaining the appropriate
current carrying capacity.  IPC-2222 outlines the calculations for
correct size and number of the spokes.  I had a hard time convincing
people here to use them, but once we did the assemblers were successful
in hand soldering these connections without preheating the boards or
using two soldering irons.  The thermal reliefs also improved our
soldering on those boards going through wave solder.

I hope this helps.  Good luck.

Phil Nutting
Design for Manufacturing Engineer

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bill Dworak
Sent: Thursday, January 25, 2007 3:01 PM
To: [log in to unmask]
Subject: [TN] Assemble question

I am in need of some help with regards to assemble. I am a PCB
manufacture and have built a group of boards for one of my accounts and
they are having issues assembling and have asked me for help on the
issues they are having.
 The product is 4 layer board power and ground planes with 2 OZ copper
inner layers the outer layers are 5 OZ copper. What is happening is that
because of the construction of the board it is acting like a big heat
sink and this is where the problems are coming from. These are old
through hole designs they are assembling them by hand they are heating
the irons way up causing surface issues on the boards and in some cases
lifting of pads is resulting when extreme heat is applied they are
heating them up a lot because of all the copper and as I am being told
the solder is not melting the way that it should.
 Any suggestions to make this a smooth build ?
 Thank you.

Bill Dworak













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