Surface mount assembly (SMT) features a crucial role to experience in the New service Introduction (NPI) process for electronics manufacturing.
Our prime amount of automation from the SMT methodology offers a variety 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 for an electronics manufacturing services (EMS) provider might be divided into four key stages:
Solder Paste Printing
Pick and set
Oven Profiling
Automated Optical Inspection (AOI)
Based on the complexity with the design, or perhaps your own outsourcing strategy, your product could go through all these processes subsequently, or you might discover that you just omit a stride or two.
We want to highlight the actual attributes, and also the vital importance, with the solder paste printing process on your NPI.
Attempting to your specifications
The first step to your EMS provider can be to analyse the printed circuit board (PCB) data that’s specific to your order, to ensure that they find the required stencil thickness and the the most appropriate material.
Solder paste printing is easily the most common technique of applying solder paste to a PCB. Accurate solder paste application is hugely important in avoiding assembly defects that may possess a knock on effect further on the production process. So it’s vital that key stage is correctly managed and controlled from your EMS partner.
Solder paste is actually powdered solder which was suspended within a thick medium called flux. The flux acts as a type of temporary adhesive, holding the constituents available until the soldering process begins. Solder paste is applied on the PCB employing a stencil (generally metal, but occasionally nickel,) then as soon as the solder is melted it forms an electrical/mechanical connection.
The thickness in the stencil is exactly what determines the total number of solder applied. For a few projects it might be necessary to have a lot of thicknesses in various areas from the one stencil (known as a multi-level stencil).
Another primary factor to take into account within the solder printing process is paste release. The right form of solder paste needs to be selected dependant on how big the apertures (or holes) inside the stencil. When the apertures are very small, by way of example, then the solder paste could be quite likely going to staying with the stencil and never adhering correctly for the PCB.
Managing the rate of paste release however can be managed, either by causing changes for the kind of the aperture or by reducing the thickness with the stencil.
The kind of solder paste that is utilized also can impact on the final print quality, therefore it is imperative that you select the appropriate mix of solder sphere size and alloy to the project, and help it become mixed for the correct consistency before use.
Ensuring quality
After the stencil has become designed and your EMS partner is preparing to generate the first PCB, they will next want to think about machine settings.
Put simply, the flatter you can maintain the PCB through the printing process, the higher final results is going to be. So by fully supporting the PCB in the printing stage,either through automated tooling pins or which has a dedicated support plate, your EMS provider can take away the chance for any defects for example poor paste deposit or smudging.
It’s also important to think about the speed and pressure from the squeegees through the printing process. One solution can be to get one speed to the solder paste but to possess varying examples of pressure, based on the unique specifications of the PCB and the length of the squeegee.
Cleaning the stencils, both prior to and throughout production, may also be essential in ensuring quality control. Many automatic printing machines have a system that could be set to completely clean the stencil after a fixed quantity of prints that helps to stop smudging, and prevents any blockages with the apertures.
Finally too, the printers needs to have a built-in inspection system (for example Hawk-Eye optical inspection) that may be preset to watch the use of paste throughout the whole PCB after printing.
The solder paste printing process is often a precise and detailed the one that have a significant part to experience inside the ultimate success of one’s new service. And, since this short article highlights, so much detailed jobs are prone to occur under the surface before your EMS partner solders the 1st electronic ingredient of a board.
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