Surface mount assembly (SMT) includes a crucial role to experience in the Cool product Introduction (NPI) process for electronics manufacturing.
Our prime degree of automation within 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 on an electronics manufacturing services (EMS) provider could be separated into four key stages:
Solder Paste Printing
Pick and set
Oven Profiling
Automated Optical Inspection (AOI)
With respect to the complexity from the design, or perhaps your own outsourcing strategy, your products could move through all these processes consequently, otherwise you might find that you simply omit one step or two.
We want to highlight the actual attributes, as well as the vital importance, of the solder paste printing process on your NPI.
Fitting in with your specifications
Step one for your EMS provider can be to analyse the printed circuit board (PCB) data which is specific on your order, to make sure that they select the required stencil thickness and 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 critical in avoiding assembly defects which could use a knock on effect further down the production process. So it’s vital until this key stage is correctly managed and controlled by your EMS partner.
Solder paste is actually powdered solder that is suspended in the thick medium called flux. The flux acts as a kind of temporary adhesive, holding the components in place before soldering process begins. Solder paste is applied to the PCB employing a stencil (generally stainless steel, but occasionally nickel,) then when the solder is melted it forms an electrical/mechanical connection.
The thickness from the stencil ‘s what determines the level of solder applied. For a few projects it might even be important to have a lot of thicknesses in different areas inside one stencil (known as a multi-level stencil).
Another important element to take into consideration within the solder printing process is paste release. The best sort of solder paste should be selected dependant on how big the apertures (or holes) inside the stencil. If your apertures are extremely small, as an example, then your solder paste could possibly be very likely to sticking with the stencil instead of adhering correctly for the PCB.
Controlling the rate of paste release however can easily be managed, either by making changes for the style of the aperture or by reducing the thickness of the stencil.
The kind of solder paste that is utilized may also affect the final top printing quality, so it is imperative that you find the appropriate combination of solder sphere size and alloy for that project, and to make sure it is mixed on the correct consistency before use.
Ensuring quality
After the stencil may be designed and your EMS partner is able to create the first PCB, they are going to next want to consider machine settings.
To put it differently, the flatter you can keep the PCB over the printing process, the better final results is going to be. So by fully supporting the PCB through the printing stage,either by the use of automated tooling pins or which has a dedicated support plate, your EMS provider can eliminate the possibility of any defects including poor paste deposit or smudging.
It’s also important to take into account the speed and pressure with the squeegees throughout the printing process. One solution is to get one speed for the solder paste but to possess varying numbers of pressure, in line with the unique specifications of the PCB and the whole squeegee.
Cleansing the stencils, both just before and throughout production, is likewise crucial in ensuring qc. Many automatic printing machines possess a system that may be set to wash the stencil following a fixed amount of prints which will help to stop smudging, and prevents any blockages with the apertures.
Finally too, the printers should have a built-in inspection system (like Hawk-Eye optical inspection) which may be preset to monitor a good paste through the whole PCB after printing.
The solder paste printing process is a precise and detailed the one which have a significant part to try out within the ultimate success of one’s new product. And, as this article highlights, a huge amount of detailed tasks are more likely to occur behind the curtain before your EMS partner solders the first electronic ingredient of a board.