Surface mount assembly (SMT) has a crucial role to experience inside the Awesome Introduction (NPI) process for electronics manufacturing.
The prime amount of automation from 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 separated into four key stages:
Solder Paste Printing
Pick and put
Automated Optical Inspection (AOI)
Depending on the complexity from the design, or your own outsourcing strategy, your products could move through each of these processes subsequently, or else you may find which you omit a stride or two.
We would like to highlight the actual attributes, as well as the vital importance, in the solder paste printing process on your NPI.
Working to your specifications
The first step to your EMS provider will be to analyse the pcb (PCB) data which is specific for your order, to make sure that they find the required stencil thickness and also the the best option material.
Solder paste printing is the most common approach to applying solder paste into a PCB. Accurate solder paste application is hugely crucial in avoiding assembly defects which can have a knock on effect further down the production process. Therefore it is vital that this key stage is correctly managed and controlled through your EMS partner.
Solder paste is actually powdered solder that is suspended inside a thick medium called flux. The flux behaves as a form of temporary adhesive, holding the constituents in position prior to the soldering process begins. Solder paste is applied to the PCB using a stencil (generally metal, but occasionally nickel,) then after the solder is melted it forms an electrical/mechanical connection.
The thickness from the stencil is the thing that determines the total number of solder applied. For many projects it may well even be required to have a lot of thicknesses in several areas from the 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 best type of solder paste ought to be selected dependant on how big is the apertures (or holes) from the stencil. If your apertures are very small, by way of example, then a solder paste could be very likely to sticking to the stencil rather than adhering correctly on the PCB.
Manipulating the rate of paste release however can easily be managed, either by making changes towards the form of the aperture or by reducing the thickness from the stencil.
The type of solder paste that is used can also impact on a final print quality, so it is crucial that you choose the appropriate combination of solder sphere size and alloy for the project, and also to makes it mixed on the correct consistency before use.
As soon as the stencil continues to be designed along with your EMS partner is able to generate the first PCB, they are going to next be considering machine settings.
To put it differently, the flatter you can preserve the PCB from the printing process, the higher final results will be. So by fully supporting the PCB in the printing stage,either by way of automated tooling pins or having a dedicated support plate, your EMS provider can get rid of the potential for any defects like poor paste deposit or smudging.
You’ll want to look at the speed and pressure with the squeegees through the printing process. One solution is going to be have one speed for the solder paste but to possess varying numbers of pressure, depending on the unique specifications from the PCB and also the length of the squeegee.
Cleansing the stencils, both prior to and throughout production, is likewise essential in ensuring qc. Many automatic printing machines use a system which can be set to completely clean the stencil after a fixed number of prints which assists to stop smudging, and prevents any blockages with the apertures.
Finally too, the printers should have a built-in inspection system (such as Hawk-Eye optical inspection) which is often preset to watch the presence of paste throughout the whole PCB after printing.
The solder paste printing process is really a precise and detailed one which will have a significant part to play within the ultimate success of your respective new service. And, simply because this post highlights, a lot of detailed jobs are planning to take place behind the curtain before your EMS partner solders the very first electronic component to a board.