Surface mount assembly (SMT) includes a crucial role to experience within the New service Introduction (NPI) process for electronics manufacturing.
Our prime amount of automation inside SMT methodology comes with a selection of advantages, from automatic correction of errors, to simpler and faster assembly, better mechanical performance, increased production rates and reduced labour costs.
The SMT assembly process on an electronics manufacturing services (EMS) provider may be broken down into four key stages:
Solder Paste Printing
Automated Optical Inspection (AOI)
With respect to the complexity in the design, or maybe your own outsourcing strategy, your products could go through each one of these processes in turn, or perhaps you could find that you omit a stride or two.
We should highlight the specific attributes, as well as the vital importance, with the solder paste printing process for the NPI.
Attempting to your specifications
Step one for your EMS provider is to analyse the pcb (PCB) data that is certainly specific in your order, to ensure that they select the required stencil thickness along with the most suitable material.
Solder paste printing is the most common approach to applying solder paste to some PCB. Accurate solder paste application is hugely critical in avoiding assembly defects which can have a very knock on effect further around the production process. So it’s vital until this key stage is correctly managed and controlled through your EMS partner.
Solder paste is basically powdered solder which has been suspended in the thick medium called flux. The flux provides for a kind of temporary adhesive, holding the components in place prior to the soldering process begins. Solder paste is applied on the PCB using a stencil (generally stainless steel, but occasionally nickel,) then when the solder is melted it forms an electrical/mechanical connection.
The thickness with the stencil is the thing that determines the level of solder applied. For a lot of projects it could be also necessary to have a lot of thicknesses in several areas from the one stencil (known as a multi-level stencil).
Another key factor to take into account within the solder printing process is paste release. The right kind of solder paste ought to be selected based on how big is the apertures (or holes) within the stencil. When the apertures are very small, for instance, then this solder paste could possibly be quite likely going to sticking with the stencil instead of adhering correctly towards the PCB.
Governing the rate of paste release however can be simply managed, either start by making changes towards the form of the aperture or by reducing the thickness of the stencil.
The type of solder paste that is used also can influence on a final top printing quality, so it’s important to pick the appropriate blend of solder sphere size and alloy to the project, and make sure it is mixed to the correct consistency before use.
Once the stencil may be designed and your EMS partner is getting ready to generate the first PCB, they’re going to next be thinking about machine settings.
Put simply, the flatter you can maintain the PCB from the printing process, the higher the end result will likely be. So by fully supporting the PCB in the printing stage,either by the use of automated tooling pins or using a dedicated support plate, your EMS provider can take away the chance of any defects including poor paste deposit or smudging.
It’s also important to take into account the speed and pressure in the squeegees throughout the printing process. One solution is to get one speed for that solder paste but to get varying numbers of pressure, in line with the unique specifications of the PCB along with the whole squeegee.
Washing the stencils, both just before and throughout production, is likewise crucial in ensuring quality control. Many automatic printing machines have a system that could be set to wash the stencil following a fixed variety of prints which helps to avoid smudging, and prevents any blockages with the apertures.
Finally too, the printers must have a built-in inspection system (like Hawk-Eye optical inspection) which can be preset to evaluate the presence of paste over the whole PCB after printing.
The solder paste printing process is really a precise and detailed the one which have a significant part to play within the ultimate success of your respective awesome. And, because this article highlights, a lot of detailed jobs are prone to take place behind the scenes before your EMS partner solders the very first electronic component to a board.