Surface mount assembly (SMT) has a crucial role to learn in the Awesome Introduction (NPI) process for electronics manufacturing.
The high level of automation from the SMT methodology comes with a various 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 might be categorised into four key stages:
Solder Paste Printing
Pick and put
Oven Profiling
Automated Optical Inspection (AOI)
With respect to the complexity in the design, or maybe your own outsourcing strategy, your products could pass through each of these processes in turn, or you could find that you simply omit one step or two.
You want to highlight the precise attributes, and the vital importance, in the solder paste printing process to your NPI.
Trying to your specifications
Step one on your EMS provider is to analyse the pcb (PCB) data that is certainly specific on your order, in order that they choose the required stencil thickness and also the most suitable material.
Solder paste printing is regarded as the common way of applying solder paste to some PCB. Accurate solder paste application is hugely important in avoiding assembly defects which could have a knock on effect further down the production process. Therefore it is vital that key stage is correctly managed and controlled because of your EMS partner.
Solder paste is basically powdered solder that has been suspended in the thick medium called flux. The flux provides for a type of temporary adhesive, holding the ingredients in place before the soldering process begins. Solder paste is applied on the PCB using a stencil (generally stainless-steel, but occasionally nickel,) then after the solder is melted it forms an electrical/mechanical connection.
The thickness from the stencil is exactly what determines the level of solder applied. For a few projects it may well also be required to have a lot of thicknesses in different areas within the one stencil (known as a multi-level stencil).
Another important element to take into account inside the solder printing process is paste release. The correct type of solder paste needs to be selected in relation to the size of the apertures (or holes) within the stencil. When the apertures are incredibly small, for example, then your solder paste could be quite likely going to adhering to the stencil and never adhering correctly towards the PCB.
Controlling the rate of paste release however can be managed, either start by making changes for the form of the aperture or by reducing the thickness from the stencil.
The kind of solder paste that is utilized could also impact on a final print quality, so it is important to select the appropriate combination of solder sphere size and alloy to the project, and to makes it mixed to the correct consistency before use.
Ensuring quality
When the stencil continues to be designed plus your EMS partner is getting ready to make the first PCB, they’ll next want to consider machine settings.
Quite simply, the flatter you can preserve the PCB over the printing process, the higher the final results will 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 eliminate the chance of any defects for example poor paste deposit or smudging.
You’ll want to consider the speed and pressure from the squeegees during the printing process. One solution can be to get one speed for your solder paste but to possess varying examples of pressure, using the unique specifications of the PCB as well as the entire squeegee.
Washing the stencils, both prior to and throughout production, can also be crucial in ensuring qc. Many automatic printing machines use a system that can be set to scrub the stencil from a fixed variety of prints which helps to stop smudging, and prevents any blockages with the apertures.
Finally too, the printers really should have a built-in inspection system (such as Hawk-Eye optical inspection) that may be preset to watch the use of paste throughout the whole PCB after printing.
The solder paste printing process can be a precise and detailed the one which may significant part to try out inside the ultimate success of your respective new service. And, as this blog post highlights, plenty of detailed jobs are planning to happen behind the curtain before your EMS partner solders the very first electronic component to a board.