Surface mount assembly (SMT) includes a crucial role to play within the Awesome Introduction (NPI) process for electronics manufacturing.
Our prime level of automation inside 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 might be categorised into four key stages:
Solder Paste Printing
Pick and put
Oven Profiling
Automated Optical Inspection (AOI)
With respect to the complexity of the design, or your own outsourcing strategy, your product or service could go through each one of these processes therefore, or you may find that you just omit one step or two.
We would like to highlight the precise attributes, and the vital importance, of the solder paste printing process for the NPI.
Fitting in with your specifications
The first task for the EMS provider is to analyse the printed circuit board (PCB) data which is specific in your order, to ensure they select the required stencil thickness and the the best option material.
Solder paste printing is easily the most common way of applying solder paste into a PCB. Accurate solder paste application is hugely crucial in avoiding assembly defects which may possess a knock on effect further around the production process. So it will be vital until this key stage is correctly managed and controlled through your EMS partner.
Solder paste is basically powdered solder that is suspended in the thick medium called flux. The flux provides a sort of temporary adhesive, holding the constituents in position before soldering process begins. Solder paste is applied to the PCB utilizing a stencil (generally stainless steel, but occasionally nickel,) then as soon as 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 a few projects it might even be essential to have several thicknesses in various areas within the one stencil (known as a multi-level stencil).
Another primary factor to consider in the solder printing process is paste release. The correct form of solder paste should be selected based upon how big is the apertures (or holes) inside stencil. If the apertures have become small, for instance, then a solder paste may be prone to staying with the stencil instead of adhering correctly for the PCB.
Controlling the rate of paste release however can be managed, either by causing changes on the design of the aperture or by lessening the thickness from the stencil.
The type of solder paste which is used can also influence on the final print quality, so it is important to pick the appropriate combination of solder sphere size and alloy for the project, and to make sure it is mixed towards the correct consistency before use.
Ensuring quality
Once the stencil has been designed and your EMS partner is able to make the first PCB, they are going to next be considering machine settings.
To put it differently, the flatter you can keep the PCB from the printing process, better the final results will be. So by fully supporting the PCB throughout the printing stage,either using automated tooling pins or having a dedicated support plate, your EMS provider can remove the chance for any defects for example poor paste deposit or smudging.
It’s also important to consider the speed and pressure with the squeegees during the printing process. One solution can be to get one speed for your solder paste but to possess varying examples of pressure, using the unique specifications of the PCB and also the whole squeegee.
Cleansing the stencils, both before and throughout production, is likewise essential in ensuring quality control. Many automatic printing machines have a system that may be set to completely clean the stencil after having a fixed amount of prints which will help to avoid smudging, and prevents any blockages in the apertures.
Finally too, the printers needs to have a built-in inspection system (like Hawk-Eye optical inspection) which can be preset to evaluate the existence of paste throughout the whole PCB after printing.
The solder paste printing process is a precise and detailed the one which may significant part to try out from the ultimate success of one’s awesome. And, simply because this article highlights, plenty of detailed jobs are likely to happen behind the curtain before your EMS partner solders the first electronic element of a board.