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Heated Flux Dispense for Pre-Clad Boards

IP.com Disclosure Number: IPCOM000117663D
Original Publication Date: 1996-Apr-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Stirpe, MB: AUTHOR

Abstract

It is desirable to retain parts and modules on pre-clad (pre-soldered) pads on a receiving circuit board during conveyor transport by the use of low viscous, low tack flux. If a higher tack and viscous flux is used, the mozzle tip of the flux dispensing mechanism may become clogged, resulting in pads not being properly fluxed or too much stringing of the flux.

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Heated Flux Dispense for Pre-Clad Boards

      It is desirable to retain parts and modules on pre-clad
(pre-soldered) pads on a receiving circuit board during conveyor
transport by the use of low viscous, low tack flux.  If a higher tack
and viscous flux is used, the mozzle tip of the flux dispensing
mechanism may become clogged, resulting in pads not being properly
fluxed or too much stringing of the flux.

      In order to dispense high tack, high viscous flux, a small tip
heater in the dispensing mechanism may be used.  Conventional nozzle
tip heaters were not found to be effective.  A special aluminum
washer surrounding and adjacent to the tip and heated by the heater
element was designed in order to allow intimate contact between the
tip and the heater.  This modified dispensing mechanism allows the
flux to be dispensed at any desired rate with no misses of pads or
excessive stringing or residue of flux.  The components are held on
their pads during conveyor transport and reflow.  Parts were held on
cards having dome pads as well as conventional flat stenciled pads.
The special heater mechanism reduces the viscosity of the flux as it
is being dispensed.  After the flux reaches the pad, the original
flux viscosity and tack return.