SMT / Finishing

ASSEMBLY OF PCB PROTOTYPES

SMT Finishing

Once the circuit board has been depaneled, assembly of the PCB prototypes can proceed. From application of solder paste to the placement of each individual Surface Mount Technology (SMT) component, LPKF provides low-cost and proven processes to create an electrically functional product in a few simple steps. 

Surface Mount Technology

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.

THE FINAL ASSEMBLY

Soldering Mask Coating

Solder mask coating protects the surfaces and conductive traces on a circuit board and prevents it from being covered with excess solder which could result in short-circuiting.

The LPKF ProMask is an easy-to-apply green solder mask ideal for SMT prototypes with small trace spacings. A film template is first created using LPKF CircuitPro. The solder mask is applied on the board and predried in the hot air oven. Aligning the film template over the board exposes the regions where the film template is not printed.

A development bath is then prepared to remove the solder mask from the unexposed regions. The solder mask is then cured and oxidation residues are removed from the board.

Solder Paste Printing

PCB stencils could be used to ensure the solder paste goes exactly where it is supposed to. LPKF's Stencil Cutting Machines creates stencils to allow for easy solder paste applications, and the LPKF ProtoPrint S is a manual stencil printer for creating SMT prototypes in small batches.

Simply secure the board onto the LPKF ProtoPrint S and align the stencil accurately. Solder paste is then applied evenly using a squeegee and the board is released, with the solder paste in the right location. 

SMD Assembly 

For complex SMD assembly, LPKF offers the ProtoPlace E4 and ProtoPlace S4 pick & place systems for precise assembly of PCBs with fine-pitch components.

A vacuum needle removes the SMD component from an antistatic bin or a feeder. The vacuum needle is mounted to a manipulator, which helps with accurate positioning. The SMD component is manually moved along or rotated about the X-axis and the Y-axis. The optional camera and an LCD colour monitor facilitate positioning. The component is then accurately lowered onto the PCB. 

Reflow Soldering

The LPKF ProtoFlow S4 compact hot-air oven allows device for RoHS-compliant lead-free reflow soldering. The reflow oven heats up the entire board, allowing the solder paste on the board to melt and fuse the components onto the board.

At the end of the process, the active cooling with the chamber closed prevents uncontrolled temperature fluctuations in the material. Through an outlet opening, any fumes or gases generated in the process is then safely discharged to an external system. 

Solder Paste Application

LPKF ProtoPrint S4

LPKF ProtoPrint S4

SMT stencil printer for fine pitch SMD prototyping

SMD Assembly

LPKF ProtoPlace S

LPKF ProtoPlace S

PCB Prototyping Machine for precision placement of fine pitch components

Reflow Soldering

LPKF ProtoFlow E

LPKF ProtoFlow E

Successful soldering in minutes with manual operation and higher control

LPKF ProtoFlow S/N2

LPKF ProtoFlow S/N2

Compact and versatile convection oven for lead-free reflow soldering

Solder Resist and Legend Printing

LPKF ProMask and ProLegend

LPKF ProMask and ProLegend

Easy-to-apply solder resist mask and assembly printing