TECHNET Archives

May 2001

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Condense Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Content-type:
text/plain; charset=us-ascii
Sender:
Subject:
From:
"<Peter George Duncan>" <[log in to unmask]>
Date:
Thu, 31 May 2001 10:03:41 +0800
MIME-Version:
1.0
X-To:
Reply-To:
"TechNet E-Mail Forum." <[log in to unmask]>, [log in to unmask]
Parts/Attachments:
text/plain (118 lines)
Have you micro-sectioned a board to ensure that it complies with spec? Is
the plating in the through-holes of the correct thickness and quality?
i.e. there are no 'smears' left after the board drilling, as these would
cause plating defects.

   a.  Insufficient wetting in PTH's can be caused by poor plating, boards
   are too cool, wrong flux (what are you using?), contamination of hole
   walls, to name but some.
   Poor plating - talk to your supplier. Boards too cool - heat soak the
   boards at about 100 deg C for about an hour (or two hours if you an
   afford the time). You may find, if the boards aren't kept heated durig
   the soldering operation, that you will have to return the boards to the
   oven every half hour or so to re-heat them. This should not be done more
   than twice, or the board will suffer too much thermal stress.   Wrong
   flux - I don't know what you're using, but presume it is an RMA flux
   whose residues will have to be washed off after soldering. Contamination
   - depends on what it is. Either clean the boards thoroughly before
   soldering and then bake to dry them out, or talk again to your PCB
   supplier about supplying cleaner boards.
   If there are no other problems with the boards, heating them will
   probably be the answer, as it would prevent the solder from solidifying
   too soon. If soldering to a cold board, the solder will freeze on the
   surface of the hole walls, while the hotter core will travel a bit
   further before it, too, solidifies. This will give the appearance of
   non-wetting. See above.
   Flux, of course has an effect on the wetting action, but try heating the
   boards first.
   Hole size won't affect wetting. If it is too large, though, it may not
   hold the solder. This will be noticeable either because the solder has
   fallen out completely, or there will be a 'bump' or stalagtite at the
   solder side of the hole and a well at the component side. If you have
   been following board design guidelines, though, for the types of
   components you are using, you shouldn't be having this problem.

Hope this helps a bit.

Pete Duncan





                    "S. Miller"
                    <CircuitekAsi        To:     [log in to unmask]
                    [log in to unmask]>           cc:     (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
                    Sent by:             Subject:     [TN] Insufficient Solder Fillet in a PTH
                    TechNet
                    <[log in to unmask]
                    ORG>


                    05/30/01
                    07:39 PM
                    Please
                    respond to
                    "TechNet
                    E-Mail
                    Forum.";
                    Please
                    respond to
                    CircuitekAsia






Dear Technetters,

My company has been conducting studies on implementing the use of robotic
soldering in our assembly process.

Whilst experimenting with such equipment, we found our product from our PCB
source to have problems; namely insufficient wetting in the PTH or
(insufficient solder fillet in the PTH).

As we have never seen this problem before, we are no evaluating the root
cause to rule out whether or not it is equipment related.

Your advise on the following matters would be truly appreciated:

a.  What causes insufficient wetting/solder fillet in a PTH?
b.  What are the corrective actions for insufficient wetting/solder fillet
in
a PTH?
c.  Would preheating the PCB's eliminate this problem?
d.  Does the selection of flux have an influence on proper wetting/solder
fillet of a PTH?
e.  Does the size of a hole influence whether or not proper wetting/solder
fillet in a PTH is achieved?

Any and all responses would be truly appreciated.

---------------------------------------------------------------------------------

Technet Mail List provided as a free 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 Technet
To temporarily halt delivery of Technet send the following message: SET
Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases >
E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
ext.5315
---------------------------------------------------------------------------------

---------------------------------------------------------------------------------
Technet Mail List provided as a free 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 Technet
To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------

ATOM RSS1 RSS2