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August 1999

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Subject:
From:
Jorge Engenharia <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 11 Aug 1999 09:38:04 -0400
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text/plain (113 lines)
Deepak

   If you are using infrared oven maybe the shadowing effect will disturb
the heat distribution to some parts. The time at 235 oC is too long and is
discolouring the PCB. The best way is profile the board and try match the
solder ring thermal requirements ( ramp up, pre heating to flux ativation,
peak temperature, time above liquidous, etc .. ). Distribute thermocouples
through the board and figure out if heat transfer is OK.

Thanks
Jorge Dourado de Santana
Maintenance / Process Engr
Microtec - Brazil


> -----Original Message-----
> From: [log in to unmask]
> [SMTP:[log in to unmask]]
> Sent: 11 de Agosto de 1999 10:12
> To:   [log in to unmask]
> Subject:      [TN] Solderability
>
> Deepak,
> seems as you have a direct-radiating IR-oven and too long exposure. What
> if you use an ordinary convection heat oven and just one minute exposure
> ?(maybe your board mass does not fit that short time). Many factors that
> you don't mention: solder mask? pin finish? flux preactivating? etc... I
> use Klein Wassink's book 'Soldering in Electronics' for trouble
> shooting. Recommend you to buy it even if you will get grand solutions
> these minutes from the often-seen-and-blessed-be-gurus in this
> forum./regards/Ingemar
>
>
> > Hello Technetters,
> >
> > We are doing a job of soldering around 4500 pins into a Glass Epoxy
> > Multilayer PCB of size 288 x 200 mm. The pins are first push fit into
> the
> > PCB . The pins protrude on both sides of the PCB . On once side the
> pins
> > will mate with a connector, and on the other side wires are wrapped
> on. 1
> > Solder ring ( 0.9 mm dia ) is then put over each pin . The board is
> then put
> > in a reflow over for 180 sec at 235 deg C. We find that the solder
> joint are
> > not properly formed, and the finish is quite dull. The solder ring is
> > composed of 62% Tin, 2 % Silver, 34 % Lead. The solder flows out to
> the
> > other side of the PCB , but is not quite enough. We also notice
> > discoloration of the PCB after this cycle.
> >
> > What are the issues  that we need to be looking at here, to get a
> better
> > joint with a better finish . We are completely new to this .
> >
> > Appreciate some inputs and tips on doing this
> >
> > With warm regards
> >
> > Deepak Kuriyan
> > Framatome Connectors OEN
> >
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