Surface mount assembly (SMT) has a crucial role to play in the Cool product Introduction (NPI) process for electronics manufacturing.
The top a higher level automation inside the SMT methodology supplies 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 broken down into four key stages:
Solder Paste Printing
Pick and set
Automated Optical Inspection (AOI)
With regards to the complexity in the design, maybe own outsourcing strategy, your product could move through all these processes therefore, or you might discover which you omit a step or two.
We want to highlight the precise attributes, as well as the vital importance, with the solder paste printing process for the NPI.
Trying to your specifications
The initial step for your EMS provider will be to analyse the printed circuit board (PCB) data which is specific for your order, to make sure that they find the required stencil thickness as well as the the most appropriate material.
Solder paste printing is regarded as the common technique of applying solder paste with a PCB. Accurate solder paste application is hugely important in avoiding assembly defects which can have a very knock on effect further down the production process. So it will be vital until this key stage is correctly managed and controlled because of your EMS partner.
Solder paste is basically powdered solder that has been suspended in a thick medium called flux. The flux acts as a sort of temporary adhesive, holding the ingredients set up prior to the soldering process begins. Solder paste is used on the PCB using a stencil (generally stainless-steel, but occasionally nickel,) then as soon as the solder is melted it forms an electrical/mechanical connection.
The thickness with the stencil ‘s what determines the total number of solder applied. For a few projects it may well be also required to have several thicknesses in numerous areas inside the one stencil (also known as a multi-level stencil).
Another primary factor to consider within the solder printing process is paste release. The right sort of solder paste must be selected based upon the dimensions of the apertures (or holes) inside the stencil. In the event the apertures are extremely small, as an example, then the solder paste might be very likely to staying with the stencil rather than adhering correctly towards the PCB.
Controlling the rate of paste release however can easily be managed, either by looking into making changes towards the form of the aperture or by lessening the thickness of the stencil.
The type of solder paste that is utilized also can effect on a final top printing quality, so it is crucial that you select the appropriate combination of solder sphere size and alloy to the project, and makes it mixed to the correct consistency before use.
After the stencil has become designed plus your EMS partner is getting ready to produce the first PCB, they’ll next want to think about machine settings.
Quite simply, the flatter you can keep the PCB from the printing process, the greater the end result will probably be. So by fully supporting the PCB during the printing stage,either by way of automated tooling pins or with a dedicated support plate, your EMS provider can eliminate the chance of any defects such as poor paste deposit or smudging.
It’s also important to take into account the speed and pressure of the squeegees through the printing process. One solution can be to have one speed for the solder paste but to possess varying numbers of pressure, in line with the unique specifications with the PCB as well as the whole squeegee.
Cleaning the stencils, both ahead of and throughout production, may also be crucial in ensuring quality control. Many automatic printing machines have a system that could be set to clean the stencil after a fixed quantity of prints which assists to stop smudging, and prevents any blockages with the apertures.
Finally too, the printers must have a built-in inspection system (like Hawk-Eye optical inspection) which can be preset to monitor the presence of paste throughout the whole PCB after printing.
The solder paste printing process is often a precise and detailed one which have a significant part to experience in the ultimate success of your respective new product. And, as this post highlights, a lot of detailed effort is likely to come about under the surface before your EMS partner solders the very first electronic aspect of a board.