Surface mount assembly (SMT) features a crucial role to learn from the New service Introduction (NPI) process for electronics manufacturing.

Our prime amount 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 with an electronics manufacturing services (EMS) provider may be separated into four key stages:

Solder Paste Printing
Pick and Place
Oven Profiling
Automated Optical Inspection (AOI)
Depending on the complexity in the design, or maybe your own outsourcing strategy, your products or services could move across all these processes in turn, or you might discover which you omit a measure or two.

We should highlight the specific attributes, along with the vital importance, in the solder paste printing process for the NPI.

Trying to your specifications
Step one to your EMS provider will be to analyse the pcb (PCB) data that is specific in your order, in order that they choose the required stencil thickness along with the the most suitable material.

Solder paste printing is among the most common approach to applying solder paste with a PCB. Accurate solder paste application is hugely important in avoiding assembly defects which may use a knock on effect further around the production process. So it is vital this key stage is correctly managed and controlled from your EMS partner.

Solder paste it’s essentially powdered solder which has been suspended inside a thick medium called flux. The flux acts as a form of temporary adhesive, holding the constituents in position before soldering process begins. Solder paste is applied to the PCB using a stencil (generally stainless, but occasionally nickel,) then after the solder is melted it forms an electrical/mechanical connection.

The thickness from the stencil is what determines the level of solder applied. For some projects it may well be also essential to have several thicknesses in different areas inside the one stencil (also known as a multi-level stencil).

Another important element to take into account in the solder printing process is paste release. The best sort of solder paste should be selected based on how big the apertures (or holes) within the stencil. In the event the apertures are very small, for example, then a solder paste could possibly be more prone to sticking to the stencil instead of adhering correctly for the PCB.

Managing the rate of paste release however can be easily managed, either by looking into making changes towards the design of the aperture or by reducing the thickness from the stencil.

The solder paste which is used may also impact on the last top printing quality, so it will be important to pick the appropriate mix of solder sphere size and alloy for your project, and to ensure it is mixed on the correct consistency before use.

Ensuring quality
As soon as the stencil continues to be designed and your EMS partner is getting ready to generate the first PCB, they are going to next be considering machine settings.

Put simply, the flatter you can the PCB over the printing process, better the outcome will likely be. So by fully supporting the PCB throughout the printing stage,either through automated tooling pins or using a dedicated support plate, your EMS provider can get rid of the chance of any defects such as poor paste deposit or smudging.

You’ll want to look at the speed and pressure in the squeegees in the printing process. One solution is to have one speed for your solder paste but to have varying examples of pressure, based on the unique specifications of the PCB and also the whole squeegee.

Cleaning the stencils, both before and throughout production, is likewise crucial in ensuring quality control. Many automatic printing machines use a system that can be set to scrub the stencil from a fixed quantity of prints which assists in order to avoid smudging, and prevents any blockages with the apertures.

Finally too, the printers must have a built-in inspection system (including Hawk-Eye optical inspection) that may be preset to monitor the use of paste over the whole PCB after printing.

The solder paste printing process can be a precise and detailed one that will have a significant part to learn from the ultimate success of your cool product. And, simply because this post highlights, so much detailed work is likely to happen c = continual reporting before your EMS partner solders the first electronic ingredient of a board.