By Bob Wettermann
Nano-coatings on SMT stencils which have come in to vogue recently are purported to have several benefits to the SMT stencil printing process.
One of the main benefits of these coatings, which claim to change the release characteristics of the metal, the process control is benefited. With printing inarguably being the area having the greatest number of variables related to the SMT process outcome, this can potentially has the greatest improvement on yield and reduction of defects. Specifically the benefits of the coating include reducing the ability of solder paste to smear or bridge on underside of the stencil. In addition the increased wetting characteristics impart to the SMT stencil can reduce flux “bleed” and solder balls transfer from stencil to the PCB. The outcome of this better process is a greater first pass yield.
Nano-coatings on SMT stencils which have come in to vogue recently are purported to have several benefits to the SMT stencil printing process.
One of the main benefits of these coatings, which claim to change the release characteristics of the metal, the process control is benefited. With printing inarguably being the area having the greatest number of variables related to the SMT process outcome, this can potentially has the greatest improvement on yield and reduction of defects. Specifically the benefits of the coating include reducing the ability of solder paste to smear or bridge on underside of the stencil. In addition the increased wetting characteristics impart to the SMT stencil can reduce flux “bleed” and solder balls transfer from stencil to the PCB. The outcome of this better process is a greater first pass yield.
Not only does the coating hold out the potential for increased process control but it holds out the potential benefit of increased processing efficiency. The potential for a reduction in the frequency of stencil cleaning holds out the benefit for a reduction in the SMT stencil cleaning frequency. This in turn will reduce the amount of consumables having to be replenished in order to clean the stencil.
Corresponding to these better process yields and increases in efficiency are a potential reduction in costs. Less SMT stencil cleaning has the potential for a corresponding decrease in cleaning solvent and wipes usage and cost. Better process control holds out the potential for less rework and repair costs. Finally the fewer disposals of wipes and cleaning solution remnants means that the potential for less cost in the process.
As a counterpoint these coatings have some negatives including : increased cost, increased disposal costs, it is not a “full proof solution” and it is not required for many of today’s designs given other materials and other laser processing techniques in the marketplace. The cost for each application ranges from $30 per stencil to $50 per stencil. This is for a single application of a product whose benefit wears out over time. Unlike higher end materials, which have a demonstrated benefit throughout the life of the stencil, So the nano-coating need to be reapplied over times.
Corresponding to these better process yields and increases in efficiency are a potential reduction in costs. Less SMT stencil cleaning has the potential for a corresponding decrease in cleaning solvent and wipes usage and cost. Better process control holds out the potential for less rework and repair costs. Finally the fewer disposals of wipes and cleaning solution remnants means that the potential for less cost in the process.
As a counterpoint these coatings have some negatives including : increased cost, increased disposal costs, it is not a “full proof solution” and it is not required for many of today’s designs given other materials and other laser processing techniques in the marketplace. The cost for each application ranges from $30 per stencil to $50 per stencil. This is for a single application of a product whose benefit wears out over time. Unlike higher end materials, which have a demonstrated benefit throughout the life of the stencil, So the nano-coating need to be reapplied over times.