Surface mount assembly (SMT) carries a crucial role to try out in the New service Introduction (NPI) process for electronics manufacturing.
Our prime degree of automation from the SMT methodology offers a variety 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 on an electronics manufacturing services (EMS) provider may be categorised into four key stages:
Solder Paste Printing
Pick and put
Automated Optical Inspection (AOI)
With regards to the complexity from the design, or perhaps your own outsourcing strategy, your products could pass through each of these processes subsequently, or you might find which you omit a measure or two.
We should highlight the actual attributes, as well as the vital importance, in the solder paste printing process to your NPI.
Fitting in with your specifications
The first step for your EMS provider can be to analyse the pcb (PCB) data that’s specific on your order, to ensure they pick the required stencil thickness and also the the most appropriate material.
Solder paste printing is the most common way of applying solder paste to some PCB. Accurate solder paste application is hugely important in avoiding assembly defects which can have a very knock on effect further on the production process. So it will be vital that this key stage is correctly managed and controlled through your EMS partner.
Solder paste is essentially powdered solder which has been suspended inside a thick medium called flux. The flux provides a sort of temporary adhesive, holding the ingredients set up prior to the soldering process begins. Solder paste is used to the PCB employing a stencil (generally stainless steel, but occasionally nickel,) then once the solder is melted it forms an electrical/mechanical connection.
The thickness from the stencil is exactly what determines the volume of solder applied. For many projects it might be also essential to have several thicknesses in different areas inside the one stencil (also known as a multi-level stencil).
Another main factor to consider in the solder printing process is paste release. The right type of solder paste should be selected dependant on how big is the apertures (or holes) inside stencil. If the apertures are incredibly small, by way of example, then this solder paste could possibly be very likely to sticking to the stencil and never adhering correctly for the PCB.
Manipulating the rate of paste release however can be easily managed, either by causing changes on the form of the aperture or by reducing the thickness in the stencil.
The solder paste that is used can also impact on a final top printing quality, so it will be important to find the appropriate blend of solder sphere size and alloy for that project, and to help it become mixed towards the correct consistency before use.
As soon as the stencil continues to be designed and your EMS partner is ready to generate the first PCB, they’ll next be thinking about machine settings.
Basically, the flatter you can maintain the PCB with the printing process, the higher the outcome will be. So by fully supporting the PCB during the printing stage,either by way of automated tooling pins or using a dedicated support plate, your EMS provider can remove the chance of any defects like poor paste deposit or smudging.
You’ll want to look at the speed and pressure of the squeegees during the printing process. One solution is to have one speed for your solder paste but to get varying degrees of pressure, based on the unique specifications from the PCB and the entire squeegee.
Cleaning the stencils, both prior to and throughout production, will also be essential in ensuring qc. Many automatic printing machines have a very system that can be set to completely clean the stencil after a fixed quantity of prints which assists to prevent 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 observe a good paste across the whole PCB after printing.
The solder paste printing process is really a precise and detailed one which will have a significant part to experience from the ultimate success of your respective new product. And, since this article highlights, a huge amount of detailed effort is prone to take place behind the curtain before your EMS partner solders the first electronic ingredient of a board.