Surface mount assembly (SMT) includes a crucial role to learn from the New Product Introduction (NPI) process for electronics manufacturing.
The prime level of automation within the SMT methodology provides a various 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 can be categorised into four key stages:
Solder Paste Printing
Automated Optical Inspection (AOI)
Depending on the complexity of the design, or your own outsourcing strategy, your products or services could move through these processes in turn, or you might find that you simply omit a step or two.
We should highlight the particular attributes, and the vital importance, with the solder paste printing process to your NPI.
Trying to your specifications
The first task for the EMS provider may be to analyse the printed circuit board (PCB) data that’s specific in your order, to ensure they find the required stencil thickness as well as the the best option material.
Solder paste printing is easily the most common approach to applying solder paste to some PCB. Accurate solder paste application is hugely important in avoiding assembly defects which may use a knock on effect further down the production process. So it will be vital until this key stage is correctly managed and controlled from your EMS partner.
Solder paste is basically powdered solder that has been suspended within a thick medium called flux. The flux provides a kind of temporary adhesive, holding the parts in position until the soldering process begins. Solder paste is applied for the PCB using a stencil (generally stainless-steel, but occasionally nickel,) then after the solder is melted it forms an electrical/mechanical connection.
The thickness of the stencil is exactly what determines the level of solder applied. For many projects it could be also important to have several thicknesses in different areas from the one stencil (also known as a multi-level stencil).
Another primary factor to consider within the solder printing process is paste release. The proper kind of solder paste ought to be selected dependant on the dimensions of the apertures (or holes) within the stencil. If your apertures are incredibly small, by way of example, then this solder paste could possibly be prone to staying with the stencil instead of adhering correctly towards the PCB.
Controlling the rate of paste release however can be easily managed, either by causing changes to the kind of the aperture or by lessening the thickness from the stencil.
The solder paste that is used could also affect a final print quality, therefore it is imperative that you select the appropriate combination of solder sphere size and alloy to the project, and to help it become mixed towards the correct consistency before use.
As soon as the stencil has become designed along with your EMS partner is able to produce the first PCB, they will next be thinking about machine settings.
Put simply, the flatter you can keep the PCB from the printing process, the greater the 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 of any defects such as poor paste deposit or smudging.
It’s also important to think about the speed and pressure from the squeegees throughout the printing process. One solution can be to get one speed to the solder paste but to possess varying examples of pressure, in line with the unique specifications with the PCB and also the length of the squeegee.
Washing the stencils, both ahead of and throughout production, will also be essential in ensuring qc. Many automatic printing machines possess a system that could be set to completely clean the stencil after a fixed number of prints that helps in order to avoid smudging, and prevents any blockages in the apertures.
Finally too, the printers really should have a built-in inspection system (such as Hawk-Eye optical inspection) which is often preset to evaluate a good paste across the whole PCB after printing.
The solder paste printing process is really a precise and detailed the one that will have a significant part to try out within the ultimate success of your respective awesome. And, since this article highlights, so much detailed tasks are planning to happen behind the scenes before your EMS partner solders the initial electronic component to a board.