Surface mount assembly (SMT) has a crucial role to play within the New service Introduction (NPI) process for electronics manufacturing.
Our prime level of automation from the SMT methodology provides 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 on an electronics manufacturing services (EMS) provider may be broken down into four key stages:
Solder Paste Printing
Pick and set
Oven Profiling
Automated Optical Inspection (AOI)
With regards to the complexity in the design, or maybe your own outsourcing strategy, your product or service could go through these processes consequently, or else you may find that you just omit a stride or two.
We would like to highlight the actual attributes, along with the vital importance, from the solder paste printing process on your NPI.
Trying to your specifications
The first task on your EMS provider will be to analyse the printed circuit board (PCB) data which is specific on your order, to ensure that they pick the required stencil thickness along with the most suitable material.
Solder paste printing is regarded as the common technique of applying solder paste into a PCB. Accurate solder paste application is hugely crucial in avoiding assembly defects that may possess a knock on effect further on the production process. Therefore it is vital until this key stage is correctly managed and controlled because of your EMS partner.
Solder paste is essentially powdered solder which has been suspended in the thick medium called flux. The flux provides for a type of temporary adhesive, holding the components in position until the soldering process begins. Solder paste is used on the PCB employing a stencil (generally metal, but occasionally nickel,) then once the solder is melted it forms an electrical/mechanical connection.
The thickness of the stencil is exactly what determines the volume of solder applied. For a lot of projects it may be also essential to have several thicknesses in numerous areas inside one stencil (sometimes called a multi-level stencil).
Another important element to think about within the solder printing process is paste release. The correct form of solder paste should be selected dependant on the dimensions of the apertures (or holes) inside the stencil. If the apertures are extremely small, by way of example, then your solder paste could be prone to sticking to the stencil rather than adhering correctly for the PCB.
Manipulating the rate of paste release however can be simply managed, either by causing changes towards the kind of the aperture or by reducing the thickness from the stencil.
The solder paste that is used could also impact on a final print quality, so it will be imperative that you select the appropriate mix of solder sphere size and alloy for that project, and make sure it is mixed on the correct consistency before use.
Ensuring quality
When the stencil has been designed and your EMS partner is getting ready to produce the first PCB, they’re going to next be thinking about machine settings.
Put simply, the flatter you can keep the PCB over the printing process, the greater the final results will likely be. So by fully supporting the PCB during the printing stage,either by the use of automated tooling pins or having a dedicated support plate, your EMS provider can take away the chance of any defects for example poor paste deposit or smudging.
You’ll want to take into account the speed and pressure of the squeegees in the printing process. One solution is usually to get one speed for your solder paste but to have varying levels of pressure, based on the unique specifications in the PCB and the length of the squeegee.
Cleansing the stencils, both ahead of and throughout production, will also be essential in ensuring quality control. Many automatic printing machines use a system that can be set to scrub the stencil after a fixed variety of prints that 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 (such as Hawk-Eye optical inspection) which can be preset to watch a good paste through the whole PCB after printing.
The solder paste printing process can be a precise and detailed one which may significant part to try out within the ultimate success of your respective awesome. And, because this post highlights, so much detailed effort is planning to happen c = continual reporting before your EMS partner solders the very first electronic component to a board.