Solder double-wave soldering

Double-wave systems are designed to solder mixed technology (SMD and through-hole components), consisting of a primary and so-caUed chip wave. The nozzle of the first wave is directed in the transport direction and produces a turbulent flow front across the board surface. 

VIII. LEAD-FREE WAVE SOLDERING A. Double-Wave Soldering... 

Surface-mount technology replaces previous methods of inserting component leads into plated through-holes of PWBs, wave soldering from the back side to flow solder into the holes, and simultaneously forming both mechanical and electrical connections. SMT is highly automated and currently the most widely used production process for the assembly of single-layer, double-sided, and multilayer circuit boards. 

Type II A double-sided board, with SMDs on both sides. The top side may have aU sizes of active and passive SMDs, as well as through-hole components, whereas the bottom side carries passive SMDs and small active components such as transistors. This type of board requires both reflow and wave soldering, and will require placement of bottom-side SMDs in adhesive. 

Double-sided, mixed technology (with bottomside wave soldering) ... 

Typically for oven reflow soldering, one profile board is prepared for the secondary-side reflow profile (in which only secondary-side components are mounted), then another for primary-side reflow profile (in which both secondary- and primary-side components are mounted). Another board is prepared for wave soldering (all SMDs loaded plus PTH parts). These boards also double as rework profile boards. 

Avoid double-sided wave-soldered PTH components Double-sided wave soldering is generally fraught with defects. Determine whether SMT or press-fit technology can be used to replace a second wave-soldering operation. The industry-standard preference is to restrict all wave-solderable components to one side (components inserted through the primary side) of the PWB. 

Understanding the stresses to which the assembly process exposes the PCB is fundamental in defining the acceptability criteria. Process elements such as leaded or lead-free, reflow or wave solder, double-sided reflow, hand-soldering, and rework all significantly impact the requirements of the PCB. 

Volume production of the lead-free assembly has been underway since June 1, 2001. Visteon produces about 7000 units a day with lead-free processing. The next level of complexity for future products will incorporate double-sided reflow, selective soldering, and wave soldering process implementation. Visteon received approval from Ford Motor Company to manufacture and supply its Passive Anti-Theft System transceiver module using lead-free solder [37]. 

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