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Tags: printer, SMT, stencil

The Critical Function Of Solder Paste Printing In New Product Introduction


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

The prime level of automation inside the 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
Oven Profiling
Automated Optical Inspection (AOI)
With regards to the complexity from the design, or perhaps your own outsourcing strategy, your product or service could move through these processes subsequently, otherwise you could find that you simply omit a measure or two.

We would like to highlight the specific attributes, and the vital importance, of the solder paste printing process on your NPI.

Working to your specifications
The initial step for your EMS provider is to analyse the printed circuit board (PCB) data that's specific for your order, to ensure they pick the required stencil thickness along with the the best option material.

Solder paste printing is the most common technique of applying solder paste with a PCB. Accurate solder paste application is hugely crucial in avoiding assembly defects which may have a knock on effect further down the production process. Therefore it is vital this key stage is correctly managed and controlled through your EMS partner.

Solder paste is basically powdered solder that is suspended inside a thick medium called flux. The flux provides a kind of temporary adhesive, holding the constituents set up prior to the soldering process begins. Solder paste is applied for 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 in the stencil is what determines the level of solder applied. For a lot of projects it may also be important to have a lot of thicknesses in numerous areas inside one stencil (often referred to as a multi-level stencil).

Another key factor to think about from the solder printing process is paste release. The best form of solder paste must be selected dependant on how big is the apertures (or holes) within the stencil. In the event the apertures are extremely small, by way of example, then this solder paste might be quite likely going to staying with the stencil instead of adhering correctly on the PCB.

Governing the rate of paste release however can be managed, either by causing changes for the design of the aperture or by lessening the thickness in the stencil.

The type of solder paste utilized could also effect on the last print quality, therefore it is vital that you select the appropriate blend of solder sphere size and alloy for your project, and to help it become mixed to the correct consistency before use.

Ensuring quality
When the stencil has become designed and your EMS partner is getting ready to generate the first PCB, they're going to next want to consider machine settings.

Quite simply, the flatter you can preserve the PCB through the printing process, better the end result will probably be. So by fully supporting the PCB during the printing stage,either through automated tooling pins or using a dedicated support plate, your EMS provider can eliminate the potential for any defects such as poor paste deposit or smudging.

You'll want to take into account the speed and pressure from the squeegees during the printing process. One solution is usually to get one speed for your solder paste but to get varying degrees of pressure, in line with the unique specifications in the PCB as well as the whole squeegee.

Cleaning the stencils, both prior to and throughout production, may also be crucial in ensuring quality control. Many automatic printing machines have a very system that can be set to scrub the stencil after having 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 (for example Hawk-Eye optical inspection) that may be preset to evaluate the existence of paste across the whole PCB after printing.

The solder paste printing process can be a precise and detailed the one which have a significant part to play within the ultimate success of one's cool product. And, since this post highlights, a huge amount of detailed work is more likely to come about behind the scenes before your EMS partner solders the very first electronic element of a board.
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