Surface mount assembly (SMT) features a crucial role to experience inside the Awesome Introduction (NPI) process for electronics manufacturing.
The high degree of automation from the 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 might be broken down into four key stages:
Solder Paste Printing
Pick make
Oven Profiling
Automated Optical Inspection (AOI)
With regards to the complexity in the design, or your own outsourcing strategy, your products could move across all these processes subsequently, otherwise you may find that you omit one step or two.
We should highlight the particular attributes, as well as the vital importance, in the solder paste printing process on your NPI.
Trying to your specifications
Step one for your EMS provider may be to analyse the printed circuit board (PCB) data that is certainly specific to your order, to ensure that they choose the required stencil thickness and the the most suitable material.
Solder paste printing is easily the most common technique of applying solder paste into a PCB. Accurate solder paste application is hugely important in avoiding assembly defects which could use a knock on effect further on the production process. So it’s vital that key stage is correctly managed and controlled because of your EMS partner.
Solder paste is essentially powdered solder that has been suspended in the thick medium called flux. The flux behaves as a form of temporary adhesive, holding the constituents in place prior to the soldering process begins. Solder paste is used for the PCB employing a stencil (generally stainless-steel, but occasionally nickel,) then once the solder is melted it forms an electrical/mechanical connection.
The thickness from the stencil is what determines the total number of solder applied. For a few projects it could be important to have a lot of thicknesses in numerous areas within the one stencil (also known as a multi-level stencil).
Another important element to consider inside the solder printing process is paste release. The proper sort of solder paste should be selected based on how big the apertures (or holes) inside stencil. When the apertures are very small, for example, then the solder paste could be very likely to sticking to the stencil and never adhering correctly for the PCB.
Managing the rate of paste release however can easily be managed, either by making changes towards the kind of the aperture or by lessening the thickness in the stencil.
The type of solder paste that is utilized also can influence on a final top printing quality, therefore it is vital that you choose the appropriate combination of solder sphere size and alloy for the project, and to ensure it is mixed to the correct consistency before use.
Ensuring quality
When the stencil continues to be designed as well as your EMS partner is able to create the first PCB, they will next be thinking about machine settings.
Basically, the flatter you can the PCB from the printing process, the greater the end result will probably be. So by fully supporting the PCB during the printing stage,either using automated tooling pins or which has a dedicated support plate, your EMS provider can get rid of the potential for any defects including 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 have one speed for your solder paste but to get varying levels of pressure, using the unique specifications from the PCB and also the length of the squeegee.
Cleansing the stencils, both prior to and throughout production, will also be essential in ensuring quality control. Many automatic printing machines possess a system that can be set to scrub the stencil from a fixed number of prints which helps to avoid smudging, and prevents any blockages from the apertures.
Finally too, the printers must have a built-in inspection system (including Hawk-Eye optical inspection) that may be preset to watch a good paste through the whole PCB after printing.
The solder paste printing process is a precise and detailed one which will have a significant part to experience from the ultimate success of your respective cool product. And, simply because this blog post highlights, a huge amount of detailed work is likely to occur under the surface before your EMS partner solders the very first electronic ingredient of a board.