>From: Ron Olinyk <[log in to unmask]>
>Reply-To: "TechNet E-Mail Forum." <[log in to unmask]>,              Ron
>Olinyk <[log in to unmask]>
>To: [log in to unmask]
>Subject: [TN] Hand soldering fine pitch SMT
>Date: Wed, 27 Nov 2002 15:48:30 -0600
>
>Can anyone recommend good soldering technique for
>hand assembly of 20mil pitch devices and 0603, 0402
>SMT chips? We are looking at doing some protoype
>assembly on some fairly dense (and small) pcbs. We
>were thinking of using solderpaste and one of those
>portable solder pens with a hot air tip ie. Weller
>Portasol.  Has anyone had success using this
>technique?
>Thanks
>Ron.

A commonly used technique that I've used successfully for fine-pitch devices
is to apply liquid flux to the pads, tack the device down at the corner
leads, then 'flood' the leads with solder, using a soldering iron with a
medium tip. You then remove the excess solder with desolder braid, and touch
up any suspect joints with a fine tip on the soldering iron.

The problem with solder paste is that it is difficult to get the right
quantity on the pads. A stencil would probably help with this, but can be
quite expensive for a prototype board. I have used solder paste with a
Weller Pyropen with 0805 passives, and ICs.

Leon
--
Leon Heller, G1HSM Tel: +44 1424 14790
Email:[log in to unmask]
My web page: http://www.geocities.com/leon_heller





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