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SMT / Finishing

Assembly of PCB prototypes and low volumes

From application of the solder paste to placement of individual components, low-cost and proven processes lead to an electrically functional product in just a few steps.

In series production, surface mount devices (SMDs) are assembled with SMT pick and place machines. Before this process takes place, paste is printed onto the pads on the board. After the SMDs have been placed on the printed circuit board, reflow soldering is performed. All processes and methods used in SMT production – adapted to the requirements of the electronics laboratory – are also available for in-house PCB prototyping.

 SMT methods for PCB prototyping


The prototyping process isn’t finished after the circuit board has been manufactured.With the subsequent processes – solder mask coating, solder paste printing, assembly, and reflow soldering – a circuit board becomes an electronic assembly.
Solder paste application

Application of solder paste on all pads on which components should be placed requires maximum precision. The LPKF ProtoPrint S stencil printer, a manual stencil printer for SMT prototyping and low-volume production, performs this task.

The mechanical resolution down to a grid size of 0.3 mm (12 mil) allows stencil printing in the ultrafine pitch range. The stencil thickness (between 100 µm and 250 µm) determines the amount of solder paste to be applied.

For PCB prototyping, milling of polyimide stencils with LPKF circuit board plotters is a genuine alternative to laser-cut steel stencils, especially from a cost perspective. Solder paste stencils (SMT stencils) can usually be milled in-house in less than ten minutes.

Component placement

For a large number of functions to be accommodated in a small space, tiny components are needed. The small dimensions of modern electronic components make manual assembly of circuit boards difficult. For the complex SMD assembly, LPKF offers users an ergonomic semiautomated pick and place system with the ProtoPlace S. The LPKF ProtoPlace S has been optimized for precise assembly with fine-pitch components. The fully equipped version features several feeders, a camera system, and a dispenser.

Reflow soldering

The compact LPKF ProtoFlow is the ideal reflow oven both for lead-containing and for RoHS-compliant lead-free reflow soldering, curing of the paste in the plated-through holes, and other thermal processes that need to be controlled precisely.

Assembly pressure and solder mask application

The solder mask coating protects the surfaces and conductive traces on a circuit board. Creation of short circuits between closely spaced pads is prevented by the professional surface finish applied in the soldering process.

LPKF ProMask is an easy-to-apply green solder mask. The professional surface finish is especially ideal for SMT prototypes with small trace spacings. LPKF ProLegend can apply any marking to the board – without using environmentally harmful wet chemical processes.

Overview of products and systems

The LPKF ProtoPlace S places the components on the solder paste pads. The system pneumatically lowers the components and places them precisely.

The ProtoFlow E is the entry-level model for reflow soldering.

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