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Flux-Free Formic Reflow

Reflow in Formic Acid Vapor

Heller has designed and built an production ready horizontal reflow oven for formic acid vapor. This new oven has been designed to meet Semi S2/S8 safety standards (including toxic gases).

  • Formic Acid has been shown to be an effective reducing agent in fluxless solder reflow
  • Excellent results demonstrated for wafer bumping application in horizontal reflow oven
  • Fluxless reflow utilizes gas phase Formic Acid (HCOOH) to replace standard fluxing agents
  • Eliminates the need for pre-reflow fluxing and post-reflow flux cleanup steps
  • No post-reflow flux clean facilitates inline application of epoxy and inline epoxy curing solution
  • Feasibility has been demonstrated with production grade oven
  • Extensive engineering efforts in safe, precision delivery of formic acid and abatement

Fluxless Reflow Advantages

  • Can use any reflow profile (e.g., tent or soak profile) with formic acid
  • Can adjust formic acid profile in oven in conjunction with thermal reflow profile
  • Includes Formic acid safety system (i.e., sensors/detectors) adheres to industry standards
  • Includes Formic acid abatement systems for Green Process Solution
  • Includes real time formic acid concentration monitor system
Formic Demo Machine

Formic Demo Machine Inside Class 10K Clean Room Florham Park, NJ.

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Formic acid sintering.

1936 MKV vacuum reflow oven.

1936 MKV - Formic Acid Horizontal Reflow Oven

Formic Acid Horizontal Reflow Oven
Formic Acid Process

Formic Acid Precision Bubbler Cabinet

  • Bubbler designed to provide consistent, reliable formic acid vapor concentration
  • Formic acid vapor concentration saturates nitrogen according to Antoine equation for a given temperature
  • Formic acid vapor concentration in the oven can be varied by bubbler temperature and nitrogen flow through bubbler
  • Bubble size is engineered with diffuser plates
  • Minimum bubble path length sets the minimum level the bubbler can operate
  • Auto refill ensures bubbler never drops below minimum level
Formic Acid Precision Bubbler Cabinet

Catalytic Burn Boxes

Catalytic Burn Boxes at each end of the oven remove all unused formic acid, carbon monoxide and hydrogen produced in the fluxless reflow process...

(Molecular hydrogen and carbon monoxide are thermal decomposition by products of formic acid...)

Catalytic Burn Boxes

Fluxless Reflow Bumping

Formic acid peak concentration 7.8%

Formic acid peak concentration 4.27%

Optical Micrographs - Formic acid peak concentration 4.27%

SAC Solder Reflow Profile

SAC Solder Reflow Profile

See Heller Reflow Oven in Action