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Benefits of Vacuum Soldering

  • Vacuum Soldering is considered a superior soldering alternative to traditional reflow belt style furnaces that generally use either flux and nitrogen atmospheres

  • Fluxless hydrogen atmospheres are considered the best way to achieve minimal voiding. 

  • It offers the advantage of a very controlled soldering environment.

  • Traditional soldering carried out using reflow furnace’s and flux

    • Result voiding >15% using large area silicon die.

    • Flux needs to be removed post solder reflow process

  • Reflow furnace’s using nitrogen atmospheres

    • No flux required

    • Will result at best 10-15% voiding

    • Nitrogen only reduces oxidation occurring during soldering

    • Parts to be extremely clean and free of all oxides (especially important if a flux not be used).

    • Requires extremely tight process control on material storage through assembly methods to minimise oxide growth or human contamination through handling.

    • Tends to be an inconsistent process resulting variable levels of voiding.

    • No post solder cleaning required

  • Reflow furnace using hydrogen atmosphere

    • No flux is required.

    • 5% to 10% voiding can be expected using hydrogen and no flux!

    • Hydrogen penetrates all surface layers to the base material and scrubs the surface clean and prepares the surfaces for soldering reflow. 

    • Handling of material and jigs is again extremely important (as it is with any process and graphite boats should NEVER be touch with out wearing gloves!).

    • The plus here is that no cleaning is required post soldering!

  • Transys Vacuum Soldering Process

    • Uses hydrogen (as a forming gas) in conjunction with vacuum down to pressure levels 25-50 Torr

    • Results the best solder joint achievable and tends to be quoted as “void-free”.

    • Hydrogen penetrates all surface layers to the base material and scrubs the surface clean and prepares the surfaces for soldering reflow.

    • As solder becomes liquidus the chamber is reduced in pressure before being backfilled allowing the joint to be maintained at the desired temperature during its state transitions from liquidus to solidus and allows the use of changing pressure to “work” the joint and hence minimise voiding!

    • Handling of material and jigs is again extremely important (as it is with any process and graphite boats should NEVER be touch with out wearing gloves!)

    • The plus here is that no cleaning is required post soldering!

      Vacuum soldering has long been a common joining technique for various applications, mainly dealing with hard soldering (brazing) without flux, where vacuum is used as an atmosphere, which sufficiently prevents oxidation through low residual partial gas pressures and partially removes oxides. The application in electronics manufacturing, where predominantly soft solders are used, is however rather restricted, where at reasons for using vacuum in soldering electronics are the possibility for fluxless soldering and the potential to reduce or prevent trapped gas volumes within the solder joint (voids).

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Transys Electronics Limited
3 Forge Mills Park, Station Road, Coleshill, Warwickshire, B46 1JH, England
Telephone: 44 (0) 1675 437609 Facsimile: 44 (0) 1675 466057 email: info@transyselectronics.com
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