Surface mount assembly (SMT) carries a crucial role to learn from the New service Introduction (NPI) process for electronics manufacturing.
Our prime level of automation inside SMT methodology offers a number 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 on 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 perhaps your own outsourcing strategy, your products could move across all these processes therefore, or you might discover that you omit a stride or two.
You want to highlight the particular attributes, as well as the vital importance, from the solder paste printing process for your NPI.
Working to your specifications
Step one for the EMS provider may be to analyse the pcb (PCB) data which is specific in your order, to ensure they pick the required stencil thickness and also the the most suitable material.
Solder paste printing is the most common approach to applying solder paste with a PCB. Accurate solder paste application is hugely important in avoiding assembly defects which can have a very knock on effect further around the production process. So it’s vital that this key stage is correctly managed and controlled from your EMS partner.
Solder paste is essentially powdered solder which was suspended in the thick medium called flux. The flux provides for a sort of temporary adhesive, holding the constituents in position before the soldering process begins. Solder paste is applied towards the PCB using a stencil (generally metal, but occasionally nickel,) then after the solder is melted it forms an electrical/mechanical connection.
The thickness with the stencil is the thing that determines the level of solder applied. For many projects it could be important to have several thicknesses in numerous areas from the one stencil (often referred to as a multi-level stencil).
Another primary factor to take into account in the solder printing process is paste release. The proper sort of solder paste needs to be selected in relation to the size of the apertures (or holes) from the stencil. When the apertures have become small, for instance, then the solder paste may be very likely to sticking to the stencil and never adhering correctly to the PCB.
Governing the rate of paste release however can be managed, either by looking into making changes on the kind of the aperture or by reducing the thickness from the stencil.
The kind of solder paste utilized can also influence on the ultimate top printing quality, so it’s crucial that you choose the appropriate mixture of solder sphere size and alloy to the project, and also to ensure it is mixed on the correct consistency before use.
When the stencil continues to be designed as well as your EMS partner is ready to produce the first PCB, they’ll next be thinking about machine settings.
Put simply, the flatter you can maintain the PCB through the printing process, the greater final results will be. So by fully supporting the PCB during the printing stage,either through automated tooling pins or which has a dedicated support plate, your EMS provider can remove the possibility of any defects like poor paste deposit or smudging.
It’s also important to think about the speed and pressure from the squeegees during the printing process. One solution is to get one speed for the solder paste but to own varying numbers of pressure, using the unique specifications with the PCB as well as the length of the squeegee.
Cleaning the stencils, both ahead of and throughout production, may also be crucial in ensuring quality control. Many automatic printing machines have a very system that can be set to wash the stencil after a fixed amount of prints which helps in order to avoid smudging, and prevents any blockages with the apertures.
Finally too, the printers really should have a built-in inspection system (for example Hawk-Eye optical inspection) that may be preset to watch a good paste over the whole PCB after printing.
The solder paste printing process is really a precise and detailed the one which will have a significant part to play from the ultimate success of the cool product. And, since this post highlights, a huge amount of detailed work is planning to occur behind the curtain before your EMS partner solders the first electronic ingredient of a board.