Solder Paste Stencils

 

Precision electrical pcb assembly attributes to a good Solder Paste Stencil, which deposits appropriate

solder paste (tin cream) onto the bare printed circuit boards to establish the electrical connections. To

meet more and more pcb assembly demand with high-density and smaller parts, Shenzhen MAD PCB and PCBA Manufacturer started to produce SMT PCB Stencils since 2012.

 

As a SMT Stencil Manufacturer, all stencils of MADPCB are 100% laser-cut and made of 304 stainless steel with extremely smooth holes that provide the best solder paste release. The frameless and framed SMT stencils in various sizes are provided to accommodate your solder paste printer and stencil requirements.

 

Experienced assemblers know that the stencil foil thickness and aperture size joint control the volume of

solder paste printed on the circuit boards. A lack of paste causes insufficient solder joint. Too much paste

causes solder balling, bridging and tomb-stoning.

 

Material

Foil: 304 stainless steel

Frame: Aluminum

Stencil Size

370x470mm [14.5’’x18.5’’]

420x520mm [16.5’’x20.5’’]

550x650mm [22.0’’x25.5’’]

735x735mm [29.0’’x29.0’’]

*other size can be customized.

*long 1600mm SMT Stencil can be provided.

Stencil Type

SMT Stencil [Framed SMT Stencil]

SMT Stencil Foil [Frameless SMT Stencil]

Foil Thickness

0.10mm (4mil)

0.12mm (5mil)

0.13mm (6mil)

0.15mm (7mil)

0.18mm (8mil)

0.20mm (10mil)

Lead Time

1-2 working days


1-2.JPG      2-2.JPG            

                           Solder Paste SMT Stencil                                                     SMT Stencil Foil


The stainless steel foil thickness is chosen upon the part types being placed and soldered on the circuit

board. Rules should follow as below,


*Aspect Ratio = Stencil Thickness / Aperture Width = T/W ≥1.5

*Area Ratio = Aperture Area / Aperture Walls Area = (L x W) / [2 x (L + W) x T]   ≥0.6

*Circular Openings = Diameter / (4 x foil thickness) ≥0.66

 


General Aperture Design Guidelines for Surface-Mount Devices:

Part

Type

Pitch

Part

Footprint

Width

Pad

Footprint

Length

Aperture

Width

Aperture

Length

Stencil

Thickness

Range

Aspect

Ratio

Range

Area

Ratio

Range

PLCC

1.25mm

[49.2mil]

0.65mm

[25.6mm]

2.00mm

[78.7mil]

0.60mm

[23.6mil]

1.95mm

[76.8mil]

0.15-0.25mm

[5.91-9.84mil]

2.3-3.8

0.88-1.48

QFP

0.65mm

[25.6mil]

0.35mm

[13.8il]

1.50mm

[59.1mil]

0.30mm

[11.8mil]

1.45mm

[57.1mil]

0.15-0.175mm

[5.91-6.89mil]

1.7-2.0

0.71-0.83

QFP

0.50mm

[19.7mil]

0.30mm

[11.8mil]

1.25mm

[49.2mil]

0.25mm

[9.84mil]

1.20mm

[47.2mil]

0.125-0.15mm

[4.92-5.91mil]

1.7-2.0

0.69-0.83

QFP

0.40mm

[15.7mil]

0.25mm

[9.84mil]

1.25mm

[49.2mil]

0.20mm

[7.87mil]

1.20mm

[47.2mil]

0.10-0.125mm

[3.94-4.92mil]

1.6-2.0

0.68-0.86

QFP

0.30

[11.8mil]

0.20mm

[7.87mil]

1.00mm

[39.4mil]

0.15mm

[5.91mil]

0.95mm

[37.4mil]

0.075-0.125mm

[2.95-3.94mil]

1.5-2.0

0.65-0.86

0402

N/A

0.5mm

[19.7mil]

0.65mm

[25.6mil]

0.45mm

[17.7]

0.60mm

[23.6mil]

0.125-0.15mm

[4.92-5.91mil]

N/A

0.84-1.00

0201

N/A

0.25mm

[9.84mil]

0.40mm

[15.7mil]

0.23mm

[9.06mil]

0.35mm

[13.8mil]

0.075-0.125mm

[2.95-3.94mil]

N/A

0.66-0.89

BGA

1.25mm

[49.2mil]

CIR

0.80mm

[31.5mil]

CIR

0.80mm

[31.5mil]

CIR

0.75mm

[29.5mil]

CIR

0.75mm

[29.5mil]

0.15-0.20mm

[5.91-7.87mil]

N/A

0.93-1.25

Fine-pitch

BGA

1.00mm

[39.4mil]

CIR

0.38mm

[15.0mil]

CIR

0.38mm

[15.0mil]

SQ

0.35mm

[13.8mil]

SQ

0.35mm

[13.8mil]

0.115-0.135m

[4.53-5.31mil]

N/A

0.67-0.78

Fine-pitch

BGA

0.50mm

[19.7mil]

CIR

0.30mm

[11.8mil]

CIR

0.30mm

[11.8mil]

SQ

0.28mm

[11.0mil]

SQ

0.28mm

[11.0mil]

0.075-0.125mm

[2.95-3.94mil]

N/A

0.69-0.92

(as per IPC-7525)

Note: Mix Assembly Technology with Surface Mount SMT Assembly and Through-hole Assembly

(Intrusive Reflow). It is desirable to have a process where SMT and THT devices can both be provided with printed solder paste, placed on or in the pcb board and reflowed together.


Process Window for Intrusive Soldering - Maximum Limits and Desirable:

--

Max Limits

Desirable

Hole Diameter

0.65-1.60mm

[25.6-63.0mil]

0.75-1.25mm

[29.5-49.2mil]

Lead Diameter

Up to hole diameter minus

0.075mm

[2.95mil]

Hole diameter minus

0.125mm

[4.92mil]

Paste Overprinting

6.35mm

[250mil]

<4.0mm

<[157mil]

Stencil Thickness

0.125-0.635mm

[4.92-25.0mil]

0.20mm

[5.91mil]

for fine-pitch


Please send us your gerber files for a quick quote now.

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