Surface mount assembly (SMT) features a crucial role to learn within the New service Introduction (NPI) process for electronics manufacturing.
The prime degree of automation inside SMT methodology supplies 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 to have an electronics manufacturing services (EMS) provider could be divided into four key stages:
Solder Paste Printing
Pick and Place
Automated Optical Inspection (AOI)
Based on the complexity with the design, or your own outsourcing strategy, your products could go through all these processes in turn, or perhaps you might discover that you omit a step or two.
You want to highlight the precise attributes, and the vital importance, with the solder paste printing process for the NPI.
Attempting to your specifications
The first task to your EMS provider can be to analyse the printed circuit board (PCB) data that is certainly specific to your order, in order that they pick the required stencil thickness and the the best option material.
Solder paste printing is regarded as the common way of applying solder paste with a PCB. Accurate solder paste application is hugely crucial in avoiding assembly defects which may have a knock on effect further around the production process. So it is vital until this key stage is correctly managed and controlled because of your EMS partner.
Solder paste it’s essentially powdered solder that has been suspended in the thick medium called flux. The flux behaves as a form of temporary adhesive, holding the parts in position prior to the soldering process begins. Solder paste is used on 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 with the stencil is exactly what determines the volume of solder applied. For a few projects it might also be necessary to have several thicknesses in numerous areas within the one stencil (also known as a multi-level stencil).
Another main factor to take into account in the solder printing process is paste release. The correct type of solder paste ought to be selected based on the dimensions of the apertures (or holes) within the stencil. If the apertures are very small, for example, then your solder paste could possibly be quite likely going to staying with the stencil and not adhering correctly on the PCB.
Governing the rate of paste release however can be managed, either by looking into making changes on the design of the aperture or by reduction of the thickness from the stencil.
The sort of solder paste utilized could also impact on the last top printing quality, so it will be imperative that you select the appropriate mixture of solder sphere size and alloy for your project, and makes it mixed on the correct consistency before use.
After the stencil has been designed along with your EMS partner is preparing to produce the first PCB, they’re going to next want to think about machine settings.
Quite simply, the flatter you can keep the PCB from the printing process, the higher the outcome is going to be. So by fully supporting the PCB throughout the printing stage,either using automated tooling pins or using a dedicated support plate, your EMS provider can take away the chance of any defects like poor paste deposit or smudging.
You’ll want to consider the speed and pressure in the squeegees throughout the printing process. One solution is to have one speed for your solder paste but to have varying levels of pressure, based on the unique specifications from the PCB as well as the entire squeegee.
Cleaning the stencils, both ahead of and throughout production, is likewise crucial in ensuring quality control. Many automatic printing machines possess a system which can be set to scrub the stencil after having a fixed number of prints which helps in order 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 can be preset to monitor a good paste over the whole PCB after printing.
The solder paste printing process can be a precise and detailed one that have a significant part to try out from the ultimate success of your cool product. And, simply because this article highlights, a lot of detailed work is planning to occur c = continual reporting before your EMS partner solders the first electronic element of a board.