Surface mount assembly (SMT) features a crucial role to try out inside the New Product Introduction (NPI) process for electronics manufacturing.
The prime degree of automation from the SMT methodology supplies a various 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 can be divided into four key stages:
Solder Paste Printing
Pick and put
Automated Optical Inspection (AOI)
Based on the complexity with the design, or perhaps your own outsourcing strategy, your products could move through each one of these processes consequently, or else you may find that you omit a stride or two.
You want to highlight the precise attributes, as well as the vital importance, with the solder paste printing process for your NPI.
Working to your specifications
Step one to your EMS provider will be to analyse the pcb (PCB) data which is specific in your order, to ensure that they choose the required stencil thickness and the the most suitable material.
Solder paste printing is regarded as the common way of applying solder paste with a PCB. Accurate solder paste application is hugely important in avoiding assembly defects which may possess a knock on effect further on the production process. So it’s vital that this key stage is correctly managed and controlled through your EMS partner.
Solder paste is basically powdered solder which was suspended inside a thick medium called flux. The flux behaves as a kind of temporary adhesive, holding the components in position before soldering process begins. Solder paste is used for the PCB by using a stencil (generally stainless-steel, but occasionally nickel,) then after the solder is melted it forms an electrical/mechanical connection.
The thickness with the stencil is what determines the volume of solder applied. For many projects it may be important to have a lot of thicknesses in numerous areas inside the one stencil (often referred to as a multi-level stencil).
Another main factor to consider within the solder printing process is paste release. The right type of solder paste needs to be selected based upon how big the apertures (or holes) from the stencil. When the apertures are incredibly small, by way of example, then this solder paste may be more prone to adhering to the stencil and never adhering correctly on the PCB.
Controlling the rate of paste release however can be simply managed, either by making changes for the form of the aperture or by lessening the thickness of the stencil.
The sort of solder paste which is used could also effect on the last print quality, therefore it is crucial that you choose the appropriate combination of solder sphere size and alloy for that project, and to help it become mixed towards the correct consistency before use.
As soon as the stencil has been designed along with your EMS partner is ready to make the first PCB, they are going to next want to think about machine settings.
To put it differently, the flatter you can maintain the PCB over the printing process, the greater the end result will likely be. So by fully supporting the PCB in the printing stage,either using 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.
It’s also important to consider the speed and pressure with the squeegees throughout the printing process. One solution is to get one speed for your solder paste but to get varying degrees of pressure, based on the unique specifications with the PCB and the whole squeegee.
Cleaning the stencils, both prior to and throughout production, will also be essential in ensuring qc. Many automatic printing machines have a system that can be set to completely clean the stencil after a fixed number of prints which helps to avoid smudging, and prevents any blockages with the apertures.
Finally too, the printers must have a built-in inspection system (such as Hawk-Eye optical inspection) which is often preset to observe the presence of paste through the whole PCB after printing.
The solder paste printing process is a precise and detailed the one which have a significant part to learn within the ultimate success of one’s new service. And, because this short article highlights, so much detailed effort is likely to occur behind the curtain before your EMS partner solders the 1st electronic ingredient of a board.