Surface mount assembly (SMT) has a crucial role to learn within the New Product Introduction (NPI) process for electronics manufacturing.
The top a higher level automation inside the SMT methodology supplies 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 for an electronics manufacturing services (EMS) provider can be broken down into four key stages:
Solder Paste Printing
Pick and put
Automated Optical Inspection (AOI)
With respect to the complexity of the design, or maybe your own outsourcing strategy, your products could move across each of these processes subsequently, or else you might find which you omit a measure or two.
You want to highlight the precise attributes, as well as the vital importance, from the solder paste printing process to your NPI.
Working to your specifications
The initial step to your EMS provider will be to analyse the pcb (PCB) data that is certainly specific for your order, to make sure that they choose the required stencil thickness along with the the most suitable material.
Solder paste printing is the most common way of applying solder paste into a PCB. Accurate solder paste application is hugely crucial in avoiding assembly defects which could use a knock on effect further around the production process. Therefore it is vital until this key stage is correctly managed and controlled because of your EMS partner.
Solder paste is actually powdered solder that has been suspended in the thick medium called flux. The flux behaves as a kind of temporary adhesive, holding the ingredients in position before soldering process begins. Solder paste is applied to the PCB using a stencil (generally stainless, but occasionally nickel,) then as soon as the solder is melted it forms an electrical/mechanical connection.
The thickness from the stencil is what determines the level of solder applied. For a few projects it could be necessary to have several thicknesses in numerous areas inside the one stencil (often referred to as a multi-level stencil).
Another important element to take into account inside the solder printing process is paste release. The best type of solder paste must be selected based on how big the apertures (or holes) from the stencil. If the apertures are incredibly small, for example, then the solder paste could be more prone to adhering to the stencil rather than adhering correctly to the PCB.
Managing the rate of paste release however can be managed, either start by making changes on the style of the aperture or by reducing the thickness of the stencil.
The sort of solder paste which is used can also influence on a final top printing quality, so it will be important to choose the appropriate mix of solder sphere size and alloy for the project, and to ensure it is mixed on the correct consistency before use.
After the stencil may be designed and your EMS partner is able to create the first PCB, they will next be thinking about machine settings.
Put simply, the flatter you can preserve the PCB from the printing process, the better the outcome will likely be. So by fully supporting the PCB through the printing stage,either using automated tooling pins or which has a dedicated support plate, your EMS provider can remove the possibility of any defects including poor paste deposit or smudging.
You’ll want to consider the speed and pressure with the squeegees during the printing process. One solution can be to have one speed to the solder paste but to get varying numbers of pressure, depending on the unique specifications of the PCB as well as the entire squeegee.
Washing the stencils, both ahead of and throughout production, may also be essential in ensuring quality control. Many automatic printing machines have a very system that may be set to clean the stencil after a fixed quantity of prints which will help in order to avoid smudging, and prevents any blockages in the apertures.
Finally too, the printers needs to have a built-in inspection system (such as Hawk-Eye optical inspection) which is often preset to evaluate the use of paste over the whole PCB after printing.
The solder paste printing process is often a precise and detailed one which will have a significant part to try out from the ultimate success of your respective awesome. And, simply because this article highlights, a huge amount of detailed effort is prone to happen behind the scenes before your EMS partner solders the initial electronic aspect of a board.