PCB Solder Paste stencils in China
Apart from all types of Printed Circuit Boards such as Prototype PCB, Aluminum PCB, HDI, Flexible PCB, Flex-Rigid PCB, High-Frequency PCB, Thick copper PCB, High-Tg PCB Zapon also specializes in manufacturing solder paste stencils in order to meet Surface Mount Technology (SMT) requirements.
Dedicated Solutions For Your PCB Solder Stencils
The openings are lasered on 100% stainless steel. Generally speaking, this kind of stencil can be produced with high quality and a high degree of precision within a short time.
Advantages: high accuracy; barely influenced by objective elements; trapezoid opening beneficial for demoulding; suitable for accurate cutting; reasonable price;
Disadvantages: relative low manufacturing speed.
The openings are etched into the metal using acid. Usually this kind of stencil offers better protection on material temper and hardness.
Advantages: one-time formation; relatively high manufacturing speed; low cost;
Disadvantages: tending to form sand clock shape or large openings; numerous manufacturing stages and accumulating errors; unsuitable for fine pitch stencils; bad for environmental protection.
The size of stencils is determined by the size of PCBs. Size of framed stencils conforms to the following simple calculation:
Width = width of PCB + 100mm
Length = length of PCB + 100mm
Size of frameless stencils conforms to the following simple calculation:
Width = width of PCB + 200mm
Length = length of PCB + 200mm
For example, if the size of a PCB is 50*50mm, then the size of its frameless stencil should be around 150*150mm and the size of its framed stencil should be around 250*250 mm.
Proper foil thickness is chosen based on the types of devices being loaded on the board. Component packages such as 0603 capacitors or 0.020” pitch SOICs, will require a thinner solder paste stencil than larger packages such as 1206 capacitors or 0.050” pitch SOICs. Solder paste stencil thickness ranges from 0.001” to 0.030”. The typical foil thickness used on the majority of boards is anywhere from 0.004” to 0.007”.
Introduction to SMT Stencils
The sole purpose of an SMT stencil is to transfer solder paste to a bare circuit board. A stainless steel foil is laser cut creating an opening for every surface mount device on the board. Once the stencil is properly aligned on top of the board, solder paste is applied over the openings (making a single pass, using a metal squeegee blade). When the stainless steel foil is separated from the board, solder paste will remain, ready for placement of the SMD. This process, as opposed to hand soldering methods, ensures consistency and saves time.
Stainless steel foil thickness and aperture opening size control the volume of paste deposited on the board. Too much solder paste causes solder balling, bridging, and tomb-stoning. A lack of solder paste creates insufficient solder joints. All of which compromise the electrical functionality of the board.
Stencil Frequently Asked Questions
01. Why would I need a PCB Stencil??
Stencils replace hand soldering of surface mount devices, and the inconsistencies created by hand soldering. They allow for direct placement of solder paste to the surface to be soldered.
02.How Do I Choose My Stencil Thickness
The stencil thickness is determined by the smallest component land pattern. If you are not sure, our design staff can choose the optimum thickness based on the data you supply.
03. What are fiducials? Do I need them on my PCB stencil?
Fiducials are alignment marks consisting of a 1mm circle surrounded by a 2mm clearance. If your screen printer is equipped with a vision system, fiducials half cut (into the thickness) of the stencil will allow for the printer to automatically align the board with the stencil. If you are manually aligning the stencil with the board, you could either fully cut the fiducials through the stencil or just use any surface mount pad to align the stencil.