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

The prime level 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 might be separated into four key stages:

Solder Paste Printing
Pick and set
Oven Profiling
Automated Optical Inspection (AOI)
With regards to the complexity of the design, or perhaps your own outsourcing strategy, your product could move across each one of these processes in turn, otherwise you might find which you omit a measure or two.

We want to highlight the particular attributes, along with the vital importance, in the solder paste printing process on your NPI.

Fitting in with your specifications
The initial step to your EMS provider may be to analyse the printed circuit board (PCB) data that’s specific for your order, in order that they select the required stencil thickness along with the the most appropriate material.

Solder paste printing is among the most common way of applying solder paste to some PCB. Accurate solder paste application is hugely important in avoiding assembly defects which can use a knock on effect further along the production process. So it is vital until this key stage is correctly managed and controlled by your EMS partner.

Solder paste is essentially powdered solder that has been suspended within a thick medium called flux. The flux provides for a sort of temporary adhesive, holding the ingredients in place until the soldering process begins. Solder paste is applied on the PCB utilizing a stencil (generally stainless steel, but occasionally nickel,) then once the solder is melted it forms an electrical/mechanical connection.

The thickness of the stencil is the thing that determines the level of solder applied. For a lot of projects it may be required to have several thicknesses in several areas within the one stencil (also known as a multi-level stencil).

Another primary factor to think about from the solder printing process is paste release. The proper sort of solder paste needs to be selected in relation to the dimensions of the apertures (or holes) inside the stencil. In the event the apertures are very small, by way of example, then your solder paste could be more prone to adhering to the stencil and never adhering correctly to the PCB.

Managing the rate of paste release however can be managed, either by looking into making changes to the form of the aperture or by lessening the thickness in the stencil.

The kind of solder paste that is utilized could also impact on the ultimate print quality, so it will be crucial that you select the appropriate mixture of solder sphere size and alloy to the project, and to make sure it is mixed towards the correct consistency before use.

Ensuring quality
After the stencil continues to be designed along with your EMS partner is able to create the first PCB, they are going to next be thinking about machine settings.

Put simply, the flatter you can maintain the PCB through the printing process, better the outcome will likely be. So by fully supporting the PCB through the printing stage,either through automated tooling pins or which has a dedicated support plate, your EMS provider can remove the possibility of any defects such as poor paste deposit or smudging.

It’s also important to take into account the speed and pressure with the squeegees through the printing process. One solution is to have one speed for that solder paste but to possess varying levels of pressure, based on the unique specifications with the PCB and the entire squeegee.

Cleansing the stencils, both prior to and throughout production, may also be crucial in ensuring quality control. Many automatic printing machines have a system that may be set to scrub the stencil after a fixed variety of prints which helps to stop smudging, and prevents any blockages in the apertures.

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

The solder paste printing process is often a precise and detailed one which will have a significant part to play in the ultimate success of your respective new product. And, as this article highlights, plenty of detailed tasks are more likely to happen c = continual reporting before your EMS partner solders the 1st electronic ingredient of a board.