Surface mount assembly (SMT) features a crucial role to play from 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 to have an electronics manufacturing services (EMS) provider might be separated into four key stages:
Solder Paste Printing
Automated Optical Inspection (AOI)
With respect to the complexity with the design, or maybe your own outsourcing strategy, your product could go through these processes therefore, or else you might find that you simply omit a stride or two.
We should highlight the specific attributes, and also the vital importance, in the solder paste printing process on your NPI.
Fitting in with your specifications
The first step for your EMS provider can be to analyse the pcb (PCB) data that is specific on your order, to make sure that they select the required stencil thickness along with the the best option material.
Solder paste printing is among the most common technique of applying solder paste into a PCB. Accurate solder paste application is hugely critical in avoiding assembly defects which can possess a knock on effect further on the production process. So it’s vital that this key stage is correctly managed and controlled from your EMS partner.
Solder paste is essentially powdered solder which was suspended in a thick medium called flux. The flux provides for a form of temporary adhesive, holding the parts set up prior to the soldering process begins. Solder paste is used to 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 of the stencil is what determines the level of solder applied. For a lot of projects it could be important to have several thicknesses in numerous areas within the one stencil (sometimes called a multi-level stencil).
Another main factor to think about in the solder printing process is paste release. The proper sort of solder paste must be selected dependant on the size of the apertures (or holes) from the stencil. When the apertures have become small, by way of example, then the solder paste might be prone to staying with the stencil instead of adhering correctly to the PCB.
Controlling the rate of paste release however can be simply managed, either start by making changes on the design of the aperture or by reduction of the thickness with the stencil.
The type of solder paste which is used can also effect on the ultimate print quality, therefore it is imperative that you pick the appropriate blend of solder sphere size and alloy for your project, and to help it become mixed for the correct consistency before use.
When the stencil has become designed as well as your EMS partner is able to create the first PCB, they’re going to next be considering machine settings.
Quite simply, the flatter you can the PCB over the printing process, the higher final results will probably be. So by fully supporting the PCB throughout the printing stage,either using automated tooling pins or having a dedicated support plate, your EMS provider can take away the potential for any defects including 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 usually to have one speed for that solder paste but to get varying degrees of pressure, in line with the unique specifications with the PCB and also the whole squeegee.
Cleaning the stencils, both ahead of and throughout production, will also be essential in ensuring qc. Many automatic printing machines have a system which can be set to completely clean the stencil from a fixed amount of prints which helps in order to avoid smudging, and prevents any blockages in the apertures.
Finally too, the printers needs to have a built-in inspection system (for example Hawk-Eye optical inspection) which may be preset to monitor the existence of paste through the whole PCB after printing.
The solder paste printing process is often a precise and detailed the one that will have a significant part to experience from the ultimate success of your new product. And, as this post highlights, plenty of detailed effort is more likely to occur behind the scenes before your EMS partner solders the very first electronic component to a board.