Surface mount assembly (SMT) carries a crucial role to try out within the New service Introduction (NPI) process for electronics manufacturing.
The high level of automation inside SMT methodology provides 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 can be categorised into four key stages:
Solder Paste Printing
Pick and set
Automated Optical Inspection (AOI)
With regards to the complexity in the design, or maybe your own outsourcing strategy, your products could pass through each of these processes therefore, or perhaps you might find that you just omit a measure or two.
We want to highlight the particular attributes, and also the vital importance, from the solder paste printing process for the NPI.
Trying to your specifications
The initial step for the EMS provider will be to analyse the printed circuit board (PCB) data that’s specific for your order, in order that they pick the required stencil thickness along with the the most suitable material.
Solder paste printing is among the most common technique of applying solder paste into a PCB. Accurate solder paste application is hugely important in avoiding assembly defects which may possess a knock on effect further down the production process. So it’s vital until this key stage is correctly managed and controlled from your EMS partner.
Solder paste it’s essentially powdered solder which was suspended in a thick medium called flux. The flux provides for a kind of temporary adhesive, holding the constituents available before the soldering process begins. Solder paste is applied for the PCB utilizing a stencil (generally stainless steel, but occasionally nickel,) then after the solder is melted it forms an electrical/mechanical connection.
The thickness in the stencil ‘s what determines the level of solder applied. For a lot of projects it might even be necessary to have several thicknesses in numerous areas from the one stencil (known as a multi-level stencil).
Another main factor to take into consideration in the solder printing process is paste release. The proper kind of solder paste must be selected in relation to how big is the apertures (or holes) inside the stencil. In the event the apertures are incredibly small, for example, then the solder paste may be more prone to sticking to the stencil and never adhering correctly on the PCB.
Manipulating the rate of paste release however can easily be managed, either by looking into making changes towards the kind of the aperture or by reducing the thickness in the stencil.
The solder paste utilized can also effect on the last print quality, so it will be vital that you choose the appropriate mix of solder sphere size and alloy to the project, and make sure it is mixed to the correct consistency before use.
When the stencil has become designed along with your EMS partner is able to create the first PCB, they’ll next be thinking about machine settings.
Quite simply, the flatter you can preserve the PCB over the printing process, better the end result is going to be. So by fully supporting the PCB during the printing stage,either through automated tooling pins or using a dedicated support plate, your EMS provider can get rid of the potential for any defects like poor paste deposit or smudging.
It’s also important to take into account the speed and pressure from the squeegees throughout the printing process. One solution is going to be have one speed for your solder paste but to have varying examples of pressure, depending on the unique specifications of the PCB along with the whole squeegee.
Washing the stencils, both before and throughout production, is likewise crucial in ensuring quality control. Many automatic printing machines have a very system that may be set to clean the stencil after a fixed quantity of prints which helps to avoid smudging, and prevents any blockages with the apertures.
Finally too, the printers needs to have a built-in inspection system (like Hawk-Eye optical inspection) that may be preset to watch the presence of paste throughout the whole PCB after printing.
The solder paste printing process can be a precise and detailed the one that have a significant part to play inside the ultimate success of one’s new service. And, simply because this post highlights, a lot of detailed tasks are more likely to take place under the surface before your EMS partner solders the first electronic component to a board.