Ron,

In response to the attached email:

We are currently in the design/prototype stage of a new product that 
requires selective wave soldering. 

On the solder side of the pwb there are many high profile devices. The 
tallest being a 140 pin SMT conn (height off the pwb is 7.5mm)

I designed a masking fixture out of a composite material ECP plus 8"L X 
8"W X 12mm thick.

Because of the tallest component, the solder side of the pwb is 8.9mm from 
the wave. The fixture creates a type of chimney which the wave must travel 
up.

Preheat didn't seem to be a problem with this fixture probably due to the 
use of 2 forced convection preheat sections and the last section having IR 
panels top and bottom.

There was no problem getting the solder to go up "the chimney" the problem 
was the solder flowing out properly. Therefore there was bridging on the 
leads closest to the exit end of the component.

Two changes were made to eliminate the bridging. 

	1. The pwb and fixture were revised where possible to allow more 
	   clearance around the leads to be soldered. 

	2. The use of an air knife on the wave soldering equipment 	   
	   eliminated bridging in all areas.

Based on these tests we purchased an Electrovert Econopak Plus for the 
production of this new product. 

Good Luck

Dan Shea
Sr. Mfg. Engineer
The Foxboro Co.
Foxboro, MA 02035
[log in to unmask]


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Date: Tue, 04 Jun 96 16:32:16 EST
From: "Hollandsworth, Ron" <[log in to unmask]>
To: [log in to unmask]
Subject: Selective Wave Soldering
Status:   

     I have been investigating selective wave soldering.  Results 
     to date have been less than desirable.  The fixture is a 
     huge heat sink, non-metal.  The objective is to keep my SMD 
     away from the wave while soldering a few through hole parts 
     and eliminate my glue operation.  The first fixture I tried 
     held the CCA very high making it difficult to get successful 
     soldering.  Current machines are two super modified, nitro 
     burning Hollis GBS Marks that have been modified with a High 
     Mass Preheats, and modified Hot Air Knives with very flat 
     CFM response curves.  Also utilizing chip waves.  I would 
     appreciate any and all recommendations or experiences you 
     would be willing to share.  Thanks in advance.  Ron From 
     Hollis Land.


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