Agreed, justo amplify this and other posts: when considering hand soldering parameters you
need to think of the total amount of heat input you are making. This is  a function of
time and temperature. The relationship is bit like a seesaw. On one end time and the other
temperature, the fulcrum in the middle is ease of soldering. Which ever one you fix or
move down the other two need to go up. As a "Rule" I suggest you should be looking to make
any hand solder joint in
around 1.5 - 2 seconds. In your case therefore you need to improve soldering ease or
increase temp to get the time down. "Soldering  ease takes in not just solderability but
things like tip shape and geometry to improve heat transfer rate.

Mike Fenner

----- Original Message -----
From: Nancy Trumbull <[log in to unmask]>
To: <[log in to unmask]>
Sent: 31 January 2000 13:03
Subject: Re: [TN] Measling after soldering


Good Morning,
      I believe that surface Measling is caused from excess  heat.
 You should check your iron tip for size compared to land and terminal.
Then  make sure that the iron is coated with solder at all times to prevent oxidation
build up.
I would think that you are having a problem with transferring the heat from the iron to
the land.
Therefore you may be holding the iron to long on the pad.
Well this may be enough to get you started.
Hope this helps and that I didn't lead you in the wrong direction.
Have a good day.
Nancy T.


>>> Goh Guan Chye <[log in to unmask]> 01/31/00 04:27AM >>>
Hi ! Technetters,

May anyone advise a measling problem after manual soldering.

We have a batch of PCBA spotted with measling after manual soldering.
These measling happen surround the areas with large copper plane. This
is a 14-layer design (2.9mm thick) with 6 layers of large copper areas
(not full plane). Due to heat sinking problem, we use solder temperature
of 350 degC and the soldering duration is about 2-3 secs. To analyse on
the problem, we wave the assembly at solder bath temp of 250 degC, no
measling found.

The question now is, this is not the first time that we manual solder
high layer count MLB with large copper plane. We did not find any
measling problem. In such case, what could it be due to ? The bare board
quality problem ? Should the bare board must be able to withstand the
manual soldering that we used ?

If the measling doesn't meet the IPC acceptance criteria, would it
affect the bare board's reliability ?

Thanks for your attention and have a nice day.

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