Surface mount assembly (SMT) carries a crucial role to learn inside the New service Introduction (NPI) process for electronics manufacturing.
Our prime a higher level automation inside 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 to have an electronics manufacturing services (EMS) provider may be categorised into four key stages:
Solder Paste Printing
Pick and put
Oven Profiling
Automated Optical Inspection (AOI)
Depending on the complexity with the design, or your own outsourcing strategy, your products could go through these processes consequently, otherwise you might discover that you simply omit one step or two.
We should highlight the particular attributes, and also the vital importance, with the solder paste printing process on your NPI.
Fitting in with your specifications
The initial step to your EMS provider is to analyse the pcb (PCB) data which is specific in your order, to make sure that they pick the required stencil thickness and also the most suitable material.
Solder paste printing is easily the most common technique of applying solder paste to some PCB. Accurate solder paste application is hugely crucial in avoiding assembly defects which could possess a knock on effect further on the production process. So it is vital that key stage is correctly managed and controlled by your EMS partner.
Solder paste it’s essentially powdered solder which has been suspended within a thick medium called flux. The flux behaves as a kind of temporary adhesive, holding the ingredients available before soldering process begins. Solder paste is applied towards the PCB employing a stencil (generally metal, 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 a lot of projects it might even be essential to have several thicknesses in numerous areas inside the one stencil (sometimes called a multi-level stencil).
Another primary factor to take into account inside the solder printing process is paste release. The proper kind of solder paste should be selected based on the size of the apertures (or holes) from the stencil. In the event the apertures are incredibly small, as an example, then your solder paste could possibly be quite likely going to adhering to the stencil instead of adhering correctly to the PCB.
Controlling the rate of paste release however can be managed, either by looking into making changes to the style of the aperture or by lessening the thickness of the stencil.
The type of solder paste utilized can also impact on the ultimate print quality, so it will be crucial that you select the appropriate combination of solder sphere size and alloy to the project, and also to make sure it is mixed for the correct consistency before use.
Ensuring quality
When the stencil continues to be designed along with your EMS partner is preparing to create the first PCB, they will next want to consider machine settings.
Quite simply, the flatter you can preserve the PCB over the printing process, the higher the end result will likely be. So by fully supporting the PCB throughout the printing stage,either through automated tooling pins or with a dedicated support plate, your EMS provider can get rid of the chance of any defects like poor paste deposit or smudging.
It’s also important to think about the speed and pressure in the squeegees through the printing process. One solution can be to have one speed to the solder paste but to possess varying degrees of pressure, based on the unique specifications with the PCB and the length of the squeegee.
Washing the stencils, both just before and throughout production, will also be essential in ensuring qc. Many automatic printing machines have a very system that can be set to wash the stencil from a fixed quantity of prints which helps to avoid smudging, and prevents any blockages from 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 evaluate the existence of paste across the whole PCB after printing.
The solder paste printing process is often a precise and detailed the one which will have a significant part to try out from the ultimate success of the awesome. And, simply because this short article highlights, so much detailed tasks are likely to take place behind the scenes before your EMS partner solders the very first electronic element of a board.
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