Surface mount assembly (SMT) carries a crucial role to learn in the Awesome Introduction (NPI) process for electronics manufacturing.
The top amount of automation from the SMT methodology provides 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 to have an electronics manufacturing services (EMS) provider may be broken down into four key stages:
Solder Paste Printing
Pick and set
Oven Profiling
Automated Optical Inspection (AOI)
Depending on the complexity from the design, or maybe your own outsourcing strategy, your products or services could move across each one of these processes in turn, or perhaps you might discover that you omit a step or two.
We should highlight the actual attributes, as well as the vital importance, in the solder paste printing process for the NPI.
Attempting to your specifications
The first step on your EMS provider may be to analyse the printed circuit board (PCB) data which is specific on your order, to ensure they find the required stencil thickness and also the the most suitable material.
Solder paste printing is the most common approach to applying solder paste to some PCB. Accurate solder paste application is hugely critical in avoiding assembly defects which may have a very knock on effect further along the production process. So it will be vital until this key stage is correctly managed and controlled by your EMS partner.
Solder paste is actually powdered solder which has been suspended within a thick medium called flux. The flux acts as a sort of temporary adhesive, holding the parts set up until the soldering process begins. Solder paste is applied on the PCB by using a stencil (generally metal, but occasionally nickel,) then when the solder is melted it forms an electrical/mechanical connection.
The thickness from the stencil ‘s what determines the total number of solder applied. For many projects it may well be essential to have a lot of thicknesses in different areas inside one stencil (also known as a multi-level stencil).
Another primary factor to think about inside the solder printing process is paste release. The right sort of solder paste needs to be selected dependant on the dimensions of the apertures (or holes) within the stencil. In the event the apertures are extremely small, for instance, then your solder paste might be quite likely going to sticking with the stencil instead of adhering correctly towards the PCB.
Governing the rate of paste release however can be easily managed, either by looking into making changes on the design of the aperture or by reduction of the thickness from the stencil.
The sort of solder paste that is used can also effect on the final top printing quality, therefore it is imperative that you choose the appropriate blend of solder sphere size and alloy for the project, also to makes it mixed for the correct consistency before use.
Ensuring quality
When the stencil continues to be designed along with your EMS partner is preparing to make the first PCB, they’ll next want to think about machine settings.
Basically, the flatter you can keep the PCB over the printing process, better final results will be. So by fully supporting the PCB in the printing stage,either by the use of automated tooling pins or with a dedicated support plate, your EMS provider can remove the potential for any defects like poor paste deposit or smudging.
You’ll want to look at the speed and pressure from the squeegees through the printing process. One solution is usually to get one speed for the solder paste but to own varying levels of pressure, based on the unique specifications from the PCB as well as the entire squeegee.
Cleaning the stencils, both before and throughout production, may also be crucial in ensuring qc. Many automatic printing machines possess a system which can be set to clean the stencil from a fixed variety of prints which assists to stop smudging, and prevents any blockages in the apertures.
Finally too, the printers must have a built-in inspection system (like Hawk-Eye optical inspection) that may be preset to monitor a good paste through the whole PCB after printing.
The solder paste printing process is a precise and detailed one that have a significant part to try out within the ultimate success of one’s awesome. And, as this blog post highlights, a huge amount of detailed work is planning to happen behind the scenes before your EMS partner solders the very first electronic ingredient of a board.
