Surface mount assembly (SMT) includes a crucial role to experience from the New Product Introduction (NPI) process for electronics manufacturing.
The high level of automation inside SMT methodology comes with 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 on 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 your own outsourcing strategy, your product could go through these processes subsequently, or you may find that you just omit one step or two.
We would like to highlight the actual attributes, and the vital importance, of the solder paste printing process to your NPI.
Trying to your specifications
The initial step on your EMS provider can be to analyse the printed circuit board (PCB) data that is certainly specific for your order, to make sure that they pick the required stencil thickness and the the best option material.
Solder paste printing is the most common method of applying solder paste with a PCB. Accurate solder paste application is hugely essential in avoiding assembly defects that may use a knock on effect further down the production process. So it is vital that this key stage is correctly managed and controlled from your EMS partner.
Solder paste is basically powdered solder which was suspended inside a thick medium called flux. The flux behaves as a sort of temporary adhesive, holding the components in position before soldering process begins. Solder paste is used on the PCB employing 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 is exactly what determines the volume of solder applied. For many projects it may be also necessary to have a lot of thicknesses in numerous areas inside the one stencil (known as a multi-level stencil).
Another main factor to take into consideration within the solder printing process is paste release. The proper kind of solder paste should be selected based upon the size of the apertures (or holes) within the stencil. In the event the apertures are extremely small, as an example, then a solder paste might be very likely to adhering to the stencil and not adhering correctly for the PCB.
Manipulating the rate of paste release however can easily be managed, either by looking into making changes for the form of the aperture or by lessening the thickness of the stencil.
The kind of solder paste that is used can also influence on a final top printing quality, so it is imperative that you choose the appropriate mixture of solder sphere size and alloy for the project, and makes it mixed to the correct consistency before use.
When the stencil has been designed along with your EMS partner is able to create the first PCB, they are going to next be considering machine settings.
Quite simply, the flatter you can preserve the PCB through the printing process, the better the end result will be. So by fully supporting the PCB throughout the printing stage,either through automated tooling pins or having a dedicated support plate, your EMS provider can get rid of the chance of any defects such as poor paste deposit or smudging.
It’s also important to consider the speed and pressure of the squeegees throughout the printing process. One solution is to get one speed for that solder paste but to have varying examples of pressure, based on the unique specifications from the PCB and the length of the squeegee.
Cleansing the stencils, both prior to and throughout production, may also be crucial in ensuring quality control. Many automatic printing machines have a very system which can be set to completely clean the stencil after a fixed quantity of prints which assists to prevent smudging, and prevents any blockages in the apertures.
Finally too, the printers must have a built-in inspection system (including Hawk-Eye optical inspection) that may be preset to watch the presence of paste over the whole PCB after printing.
The solder paste printing process is often a precise and detailed the one which will have a significant part to learn from the ultimate success of one’s awesome. And, because this blog post highlights, a lot of detailed work is likely to happen behind the curtain before your EMS partner solders the first electronic aspect of a board.