Surface mount assembly (SMT) has a crucial role to try out in the New service Introduction (NPI) process for electronics manufacturing.
Our prime level of automation within the SMT methodology provides a selection 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 with an electronics manufacturing services (EMS) provider may be categorised into four key stages:
Solder Paste Printing
Automated Optical Inspection (AOI)
Depending on the complexity with the design, maybe own outsourcing strategy, your product could go through all these processes in turn, or else you might find that you omit a measure or two.
You want to highlight the precise attributes, along with the vital importance, of the solder paste printing process to your NPI.
Trying to your specifications
The initial step for the EMS provider will be to analyse the pcb (PCB) data which is specific to your order, to ensure they find the required stencil thickness as well as the the best option material.
Solder paste printing is easily the most common approach to applying solder paste into a PCB. Accurate solder paste application is hugely essential in avoiding assembly defects which could possess a knock on effect further along the production process. So it’s vital that this key stage is correctly managed and controlled by your EMS partner.
Solder paste is basically powdered solder which has been suspended within a thick medium called flux. The flux provides for a form of temporary adhesive, holding the components set up before the soldering process begins. Solder paste is used to the PCB using a stencil (generally stainless, but occasionally nickel,) then as soon as the solder is melted it forms an electrical/mechanical connection.
The thickness in the stencil is the thing that determines the total number of solder applied. For a lot of projects it could be required to have several thicknesses in various areas from the one stencil (sometimes called a multi-level stencil).
Another important element to take into consideration from the solder printing process is paste release. The best form of solder paste needs to be selected based upon the dimensions of the apertures (or holes) inside the stencil. If your apertures have become small, for instance, then this solder paste may be quite likely going to adhering to the stencil rather than adhering correctly for the PCB.
Governing the rate of paste release however can easily be managed, either by causing changes for the style of the aperture or by lessening the thickness in the stencil.
The solder paste utilized also can effect on a final top printing quality, so it’s important to pick the appropriate blend of solder sphere size and alloy to the project, also to make sure it is mixed for the correct consistency before use.
Once the stencil continues to be designed plus your EMS partner is preparing to create the first PCB, they are going to next be considering machine settings.
Basically, the flatter you can maintain the PCB from the printing process, better the final results will be. So by fully supporting the PCB in the printing stage,either through automated tooling pins or with a dedicated support plate, your EMS provider can eliminate the chance for any defects including poor paste deposit or smudging.
It’s also important to think about the speed and pressure with the squeegees during the printing process. One solution is usually to have one speed for that solder paste but to get varying examples of pressure, in line with the unique specifications of the PCB and the whole squeegee.
Washing the stencils, both ahead of and throughout production, is likewise essential in ensuring qc. Many automatic printing machines have a very system that could be set to completely clean the stencil from a fixed quantity of prints which assists to prevent smudging, and prevents any blockages in the apertures.
Finally too, the printers should have a built-in inspection system (like 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 really a precise and detailed the one which have a significant part to try out in the ultimate success of your respective new service. And, because this post highlights, a lot of detailed effort is likely to occur behind the scenes before your EMS partner solders the very first electronic ingredient of a board.