Surface mount assembly (SMT) has a crucial role to try out inside the New service Introduction (NPI) process for electronics manufacturing.
The top amount of automation within the SMT methodology supplies 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 for an electronics manufacturing services (EMS) provider might be categorised into four key stages:
Solder Paste Printing
Automated Optical Inspection (AOI)
With regards to the complexity from the design, or maybe your own outsourcing strategy, your product or service could move through these processes in turn, or else you may find that you just omit a stride or two.
You want to highlight the particular attributes, and the vital importance, of the solder paste printing process to your NPI.
Attempting to your specifications
The first step to your EMS provider will be to analyse the pcb (PCB) data which is specific to your order, to ensure they find the required stencil thickness and also the the most appropriate material.
Solder paste printing is regarded as the common technique of applying solder paste to a PCB. Accurate solder paste application is hugely crucial in avoiding assembly defects which may have a knock on effect further on the production process. So it is vital until this key stage is correctly managed and controlled from your EMS partner.
Solder paste is basically powdered solder which has been suspended within a thick medium called flux. The flux provides a sort of temporary adhesive, holding the components in position until the soldering process begins. Solder paste is used towards the PCB using a stencil (generally stainless-steel, but occasionally nickel,) then once the solder is melted it forms an electrical/mechanical connection.
The thickness with the stencil is the thing that determines the total number of solder applied. For a few projects it may be also required to have several thicknesses in numerous areas inside one stencil (often referred to as a multi-level stencil).
Another main factor to take into account within the solder printing process is paste release. The proper kind of solder paste should be selected in relation to the dimensions of the apertures (or holes) from the stencil. When the apertures are very small, for example, then a solder paste could possibly be quite likely going to adhering to the stencil and not adhering correctly to the PCB.
Governing the rate of paste release however can be managed, either by causing changes to the style of the aperture or by reduction of the thickness with the stencil.
The kind of solder paste which is used also can effect on the ultimate print quality, so it’s important to find the appropriate mixture of solder sphere size and alloy for that project, and to make sure it is mixed to the correct consistency before use.
As soon as the stencil has been designed along with your EMS partner is preparing to make the first PCB, they’re going to next be considering machine settings.
To put it differently, the flatter you can the PCB from the printing process, better the end result will be. So by fully supporting the PCB during the printing stage,either by the use of automated tooling pins or which has a dedicated support plate, your EMS provider can remove the chance of any defects for example poor paste deposit or smudging.
It’s also important to look at the speed and pressure of the squeegees during the printing process. One solution is going to be get one speed to the solder paste but to have varying examples of pressure, in line with the unique specifications in the PCB as well as the entire squeegee.
Cleaning the stencils, both just before and throughout production, will also be essential in ensuring quality control. Many automatic printing machines have a very system that can be set to clean the stencil from a fixed amount 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 (like Hawk-Eye optical inspection) which can be preset to monitor the use of paste over the whole PCB after printing.
The solder paste printing process can be a precise and detailed one that may significant part to experience inside the ultimate success of your respective cool product. And, because this blog post highlights, plenty of detailed tasks are more likely to happen behind the scenes before your EMS partner solders the initial electronic element of a board.