Surface mount assembly (SMT) includes a crucial role to experience within the New service Introduction (NPI) process for electronics manufacturing.

The top amount of automation inside 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 to have an electronics manufacturing services (EMS) provider may be categorised into four key stages:

Solder Paste Printing
Pick and put
Oven Profiling
Automated Optical Inspection (AOI)
With regards to the complexity from the design, maybe own outsourcing strategy, your product could go through these processes subsequently, or perhaps you may find that you simply omit a measure or two.

We want to highlight the specific attributes, and the vital importance, in the solder paste printing process to your NPI.

Trying to your specifications
The initial step on your EMS provider may be to analyse the pcb (PCB) data that is specific on your order, in order that they select the required stencil thickness and the the most suitable material.

Solder paste printing is easily the most common way of applying solder paste into a PCB. Accurate solder paste application is hugely crucial in avoiding assembly defects which can use a knock on effect further on the production process. So it will be vital until this key stage is correctly managed and controlled through your EMS partner.

Solder paste it’s essentially powdered solder that is suspended inside a thick medium called flux. The flux acts as a kind of temporary adhesive, holding the constituents in position prior to the soldering process begins. Solder paste is applied to the PCB utilizing a stencil (generally metal, but occasionally nickel,) then when the solder is melted it forms an electrical/mechanical connection.

The thickness from the stencil is exactly what determines the total number of solder applied. For a lot of projects it may well be required to have a lot of thicknesses in different areas from the one stencil (also known as a multi-level stencil).

Another main factor to take into account from the solder printing process is paste release. The best sort of solder paste ought to be selected in relation to how big is the apertures (or holes) inside the stencil. If the apertures are very small, by way of example, then this solder paste could possibly be very likely to staying with the stencil and not adhering correctly towards the PCB.

Controlling the rate of paste release however can be easily managed, either start by making changes on the style of the aperture or by reduction of the thickness in the stencil.

The solder paste utilized may also influence on a final print quality, so it will be important to choose the appropriate mixture of solder sphere size and alloy to the project, and to help it become mixed towards the correct consistency before use.

Ensuring quality
When the stencil continues to be designed plus your EMS partner is preparing to generate the first PCB, they’re going to next want to consider machine settings.

To put it differently, the flatter you can preserve the PCB from the printing process, better the outcome will be. So by fully supporting the PCB throughout the printing stage,either by the use of automated tooling pins or using a dedicated support plate, your EMS provider can take away the potential for any defects such as poor paste deposit or smudging.

You’ll want to consider the speed and pressure with the squeegees throughout the printing process. One solution can be to have one speed for that solder paste but to have varying levels of pressure, using the unique specifications from the PCB as well as the entire squeegee.

Cleaning the stencils, both prior to and throughout production, can also be essential in ensuring qc. Many automatic printing machines have a system which can be set to completely clean the stencil following a fixed number of prints which will help to stop smudging, and prevents any blockages with the apertures.

Finally too, the printers needs to have a built-in inspection system (for example Hawk-Eye optical inspection) which is often preset to observe the existence of paste across the whole PCB after printing.

The solder paste printing process can be a precise and detailed one that will have a significant part to experience in the ultimate success of the awesome. And, as this blog post highlights, so much detailed tasks are planning to occur behind the curtain before your EMS partner solders the first electronic element of a board.