Surface mount assembly (SMT) includes a crucial role to learn from the New Product Introduction (NPI) process for electronics manufacturing.
The high level 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 could be categorised into four key stages:
Solder Paste Printing
Pick and put
Automated Optical Inspection (AOI)
Depending on the complexity with the design, maybe own outsourcing strategy, your product or service could go through all these processes subsequently, or you could find that you simply omit a measure or two.
You want to highlight the actual attributes, and also the vital importance, from the solder paste printing process for your NPI.
Attempting to your specifications
The initial step on your EMS provider may be to analyse the pcb (PCB) data that is specific to your order, to ensure they pick the required stencil thickness and also the most suitable material.
Solder paste printing is easily the most common way of applying solder paste to some PCB. Accurate solder paste application is hugely important in avoiding assembly defects which may possess a knock on effect further on the production process. So it is vital that this key stage is correctly managed and controlled because of your EMS partner.
Solder paste it’s essentially powdered solder that has been suspended inside a thick medium called flux. The flux behaves as a sort of temporary adhesive, holding the constituents in place until the soldering process begins. Solder paste is applied for the PCB by using a stencil (generally metal, but occasionally nickel,) then once the solder is melted it forms an electrical/mechanical connection.
The thickness from the stencil is exactly what determines the level of solder applied. For some projects it might even be essential to have a lot of thicknesses in numerous areas inside one stencil (often referred to as a multi-level stencil).
Another key factor to think about inside the solder printing process is paste release. The right kind of solder paste needs to be selected dependant on the size of the apertures (or holes) from the stencil. If your apertures have become small, for example, then your solder paste could be more prone to adhering to the stencil instead of adhering correctly for the PCB.
Governing the rate of paste release however can be easily managed, either by causing changes for the design of the aperture or by reduction of the thickness from the stencil.
The type of solder paste which is used can also influence on a final top printing quality, so it will be crucial that you pick the appropriate combination of solder sphere size and alloy for that project, and to makes it mixed towards the correct consistency before use.
When the stencil has become designed as well as your EMS partner is getting ready to make the first PCB, they will next want to consider machine settings.
Put simply, the flatter you can keep the PCB through the printing process, the better final results will probably be. So by fully supporting the PCB in the printing stage,either by way of automated tooling pins or using a dedicated support plate, your EMS provider can remove the chance for any defects like poor paste deposit or smudging.
It’s also important to think about the speed and pressure in the squeegees throughout the printing process. One solution is usually to get one speed to the solder paste but to have varying degrees of pressure, based on the unique specifications of the PCB and also the whole squeegee.
Cleansing the stencils, both prior to and throughout production, is likewise crucial in ensuring qc. Many automatic printing machines use a system that may be set to wash the stencil following a fixed amount of prints which will help to avoid smudging, and prevents any blockages of 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 observe a good paste through the whole PCB after printing.
The solder paste printing process can be a precise and detailed one which will have a significant part to play in the ultimate success of the cool product. And, because this short article highlights, so much detailed jobs are more likely to occur behind the curtain before your EMS partner solders the first electronic aspect of a board.