09/16/2023
Objective1: To be able to recollect the three main components of an SMT-PCB assembly, and
write them down or type them in, within 90 seconds.
Objective2: To be able to choose two of the three main components that are used in stencil
printing, by selecting boxes in a multiple-choice question, within 45 seconds.
Objective3: To be able to verbally name the preformed part that directs the solder paste
onto a PCB, using your voice, within 20 seconds.
Let’s focus on the manufacture of surface mount - printed circuit board assemblies using
automated equipment. That is to say, SMT-PCB assemblies for which hand placement and
hand soldering are minimal.
Furthermore, we make the distinction between the equipment and its pieces that are used
to produce the assembly, and the components that are present within the final assembly.
There are three main components that are present in a finished SMT-PCB assembly. These
are the PCB itself, the paste used for soldering, and various electronic parts. Variations and
extensions of these three basic components certainly abound; for our purpose of explanation
we’ll maintain these three. Each of the three are supplied by other manufacturers.
Depositing solder paste to the finished pads on a PCB surface is the first major step of
addition in the assembly manufacturing process. And it must be done in defined locations on
the PCB with specified thickness of the solder paste.
To accomplish this there must be some setup prior to the step, which can include material
selection, loading of material, equipment programming, and inspections of configurations
before, also product after, the step. Setup, inspection, and the value-added step are
considered together as a unit operation.
There are two predominant methods of applying solder paste to a PCB. The first, and most
widely used, is a stencil and squeegee combination; in much the same way that logos are
printed onto T-shirts. Another method is to dispense solder paste from a nozzle in small
amounts at high speed. We choose to use the stencil and squeegee method for our
description. In this method, the stencil is a preformed part that determines where paste is
deposited onto the PCB.
To summarize, there are three main components present in a finished SMT-PCB assembly.
Two of those components are used in the primary stencil printing step. In addition to those
two components, a preformed stencil is required for this step.