Surface mount assembly (SMT) has a crucial role to try out in the Awesome Introduction (NPI) process for electronics manufacturing.
Our prime degree of automation from the SMT methodology supplies 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 with 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 of the design, or maybe your own outsourcing strategy, your product or service could go through all these processes in turn, otherwise you might find that you just omit one step or two.
We should highlight the specific attributes, along with the vital importance, from the solder paste printing process to your NPI.
Working to your specifications
The first step to your EMS provider will 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 along with the the most suitable material.
Solder paste printing is easily the most common approach to applying solder paste with a PCB. Accurate solder paste application is hugely important in avoiding assembly defects which can possess a knock on effect further on the production process. So it is vital that key stage is correctly managed and controlled through your EMS partner.
Solder paste is essentially powdered solder which has been suspended within a thick medium called flux. The flux acts as a type of temporary adhesive, holding the constituents in place prior to the soldering process begins. Solder paste is used on the PCB by using a stencil (generally stainless steel, but occasionally nickel,) then when the solder is melted it forms an electrical/mechanical connection.
The thickness in the stencil is what determines the level of solder applied. For many projects it might also be necessary to have several thicknesses in different areas inside the one stencil (also known as a multi-level stencil).
Another main factor to take into consideration within the solder printing process is paste release. The correct sort of solder paste should be selected dependant on the size of the apertures (or holes) inside stencil. When the apertures are extremely small, for example, then the solder paste could be very likely to adhering to the stencil instead of adhering correctly to the PCB.
Controlling the rate of paste release however can be simply managed, either by making changes for the form of the aperture or by reducing the thickness with the stencil.
The type of solder paste utilized can also effect on a final print quality, so it will be important to pick the appropriate blend of solder sphere size and alloy for the project, also to makes it mixed on the correct consistency before use.
Ensuring quality
When the stencil may be designed and your EMS partner is preparing to produce the first PCB, they’re going to next be considering machine settings.
Put simply, the flatter you can maintain the PCB with the printing process, the greater the end result is going to be. So by fully supporting the PCB through the printing stage,either by the use of automated tooling pins or having a dedicated support plate, your EMS provider can get rid of the chance for any defects like poor paste deposit or smudging.
You’ll want to look at the speed and pressure from the squeegees during the printing process. One solution can be to have one speed to the solder paste but to get varying numbers of pressure, depending on the unique specifications with the PCB and also the whole squeegee.
Cleansing the stencils, both before and throughout production, can also be essential in ensuring qc. Many automatic printing machines have a system that could be set to clean the stencil following a fixed variety 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 may be preset to evaluate the existence of paste throughout the whole PCB after printing.
The solder paste printing process can be a precise and detailed one which will have a significant part to play from the ultimate success of your respective awesome. And, because this blog post highlights, a huge amount of detailed tasks are likely to occur behind the scenes before your EMS partner solders the first electronic component to a board.