Surface mount assembly (SMT) has a crucial role to learn inside the New service Introduction (NPI) process for electronics manufacturing.
The high degree of automation inside the SMT methodology offers 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 to have an electronics manufacturing services (EMS) provider can be separated into four key stages:
Solder Paste Printing
Automated Optical Inspection (AOI)
Depending on the complexity of the design, or perhaps your own outsourcing strategy, your products or services could go through these processes therefore, or perhaps you could find that you simply omit a stride or two.
We want to highlight the particular attributes, and also the vital importance, with the solder paste printing process on your NPI.
Fitting in with your specifications
Step one for the EMS provider can be to analyse the printed circuit board (PCB) data that is certainly specific to your order, to ensure they pick the required stencil thickness and also the the most suitable material.
Solder paste printing is easily the most common technique of applying solder paste to a PCB. Accurate solder paste application is hugely crucial in avoiding assembly defects that may possess a knock on effect further down the production process. Therefore it is vital that key stage is correctly managed and controlled through your EMS partner.
Solder paste is actually powdered solder that is suspended in a thick medium called flux. The flux provides for a kind of temporary adhesive, holding the constituents set up before the soldering process begins. Solder paste is applied for the PCB employing a stencil (generally stainless-steel, but occasionally nickel,) then after the solder is melted it forms an electrical/mechanical connection.
The thickness from the stencil ‘s what determines the level of solder applied. For a lot of projects it could even be required to have a lot of thicknesses in various areas from the one stencil (sometimes called a multi-level stencil).
Another main factor to take into consideration inside the solder printing process is paste release. The best form of solder paste needs to be selected in relation to how big is the apertures (or holes) from the stencil. If your apertures are incredibly small, as an example, then the solder paste might be more prone to adhering to the stencil instead of adhering correctly towards the PCB.
Governing the rate of paste release however can be simply managed, either by making changes for the style of the aperture or by reduction of the thickness from the stencil.
The sort of solder paste utilized could also impact on a final print quality, so it will be important to find the appropriate blend of solder sphere size and alloy to the project, and to help it become mixed to the correct consistency before use.
When the stencil may be designed as well as your EMS partner is ready to produce the first PCB, they are going to next be considering machine settings.
Basically, the flatter you can maintain the PCB from the printing process, the greater final results will probably be. So by fully supporting the PCB through the printing stage,either by the use of automated tooling pins or having a dedicated support plate, your EMS provider can take away the chance for any defects like poor paste deposit or smudging.
You’ll want to think about the speed and pressure with the squeegees through the printing process. One solution can be to get one speed for your solder paste but to get varying levels of pressure, depending on the unique specifications in the PCB along with the entire squeegee.
Cleansing the stencils, both ahead of and throughout production, can also be essential in ensuring qc. Many automatic printing machines use a system that could be set to wash the stencil after having a fixed number of prints that helps to stop smudging, and prevents any blockages in the apertures.
Finally too, the printers really should have a built-in inspection system (including Hawk-Eye optical inspection) that may be preset to watch a good paste through the whole PCB after printing.
The solder paste printing process is a precise and detailed one which will have a significant part to learn within the ultimate success of the new product. And, as this blog post highlights, so much detailed effort is planning to take place under the surface before your EMS partner solders the very first electronic aspect of a board.