ASSOCIATION CONNECTING ELECTRONICS …

1 IPC-7525 AStencil design GuidelinesDeveloped by the stencil design Task Group (5-21e) of the Assemblyand Joining Processes Committee (5-20) of IPCU sers of this publication are encouraged to participate in thedevelopment of future :IPC3000 Lakeside Drive, Suite 309 SBannockburn, Illinois60015-1249 Tel 847 847 :IPC-7525 - May 2000 ASSOCIATION CONNECTINGELECTRONICS INDUSTRIES Table of and Definitions .. *Aperture .. *Aspect Ratio .. *Area Ratio .. Paste Transfer Head .. Factor .. BGA/Chip Scale Package (CSP) .. *Fine-Pitch Technology (FPT) .. *Intrusive Soldering .. *Land .. *Overprinting .. *Pad .. *Squeegee .. BGA .. * stencil .. stencil .. *Surface-Mount Technology (SMT) .. *Through-Hole Technology (THT).

2 Pitch Technology .. 22 APPLICABLE .. 23 stencil Data .. Format .. Format .. List .. Paste Layer .. Transfer .. Stencils .. Orientation/Rotation .. Location .. design .. Size .. Size Versus Board Land Size forTin Lead Solder Paste .. Size versus Board Land Size forLead Free Solder Paste .. Aperture Chip Component .. Apertures for Combination of ChipComponents and Leaded Devices .. Technology Surface-Mount/Through-Hole (Intrusive Reflow) .. Paste Volume .. Technology Surface-Mount/Flip Chip .. stencil for Surface-Mount/Flip Chip .. stencil design .. stencil .. stencil .. stencil for Contained Paste TransferHeads .. stencil .. Fiducials .. Fiducials.

3 124 stencil .. Border .. Fabrication Technologies .. Etch .. Stencils .. Apertures .. Options .. 125 stencil of Image on Metal .. design guidelines .. 136 stencil 137 stencil USER S 138 stencil 139 END OF 13 APPENDIX AEXAMPLE ORDER 14 February 2007 IPC-7525 AiiiFiguresFigure 3-1 Area Ratio Chart Showing Recommendationsfor a 4 mil Thick stencil .. 4 Figure 3-2 Area Ratio Chart Showing Recommendationsfor a 5 mil Thick stencil .. 5 Figure 3-3 Area Ratio Chart Showing Recommendationsfor a 6 mil Thick stencil .. 5 Figure 3-4 Area Ratio Chart Showing Recommendationsfor a 8 mil Thick stencil .. 6 Figure 3-5 Cross-Sectional View of A stencil .. 6 Figure 3-6 Home Plate Aperture design .. 7 Figure 3-7 Bow Tie Aperture design .

4 7 Figure 3-8 Oblong Aperture design .. 7 Figure 3-9 Aperture design for MELF Components andChip Components .. 7 Figure 3-10 Window Pane design for Ground Plane .. 7 Figure 3-11 Glue stencil Aperture design .. 8 Figure 3-12 Chip Component and SOIC Presenton Board .. 8 Figure 3-13 Print Only Mode 15 mil Thick stencil .. 8 Figure 3-14 Glue stencil with Glue Reservoir ..9 Figure 3-15 Through-Hole Solder Paste Volume .. 9 Figure 3-16 Overprint without Step .. 10 Figure 3-17 Overprint with Step (Squeegee Side) .. 10 Figure 3-18 Overprint with Step (Contact/Board Side) .. 10 Figure 3-19 Two-Print Through-Hole stencil .. 10 Figure 3-20 Two-Print stencil for Mixed Technology .. 11 Figure 4-1 Trapezoidal Apertures .. 12 TablesTable 3-1 General Aperture design Guideline Examplesfor Selective Surface-Mount Devices (Tin LeadSolder Paste).

5 3 Table 3-2 Process Window for Intrusive Soldering -Maximum Limits Desirable .. 3 IPC-7525 AFebruary 2007ivStencil design Guidelines1 PURPOSEThis document provides guides for the design and fabrica-tion of stencils for solder paste and surface-mount adhe-sive. It is intended as a guideline only as much of the con-tent is based on the experience of stencil designers,fabricators and users. Printing performance depends onmany different variables and therefore no single set ofdesign rules can be Terms and DefinitionsAll terms and definitionsused throughout this handbook are in compliance with IPC-T-50. Definitions denoted with an asterisk (*) below arereprints from IPC-T-50. Other specific terms and defini-tions, essential for the discussion of the subject, are pro-vided *ApertureAn opening in the stencil *Aspect RatioThe ratio of the width of the aper-ture to the thickness of the stencil *Area RatioThe ratio of the area of aperture open-ing to the area of aperture BorderPeripheral tensioned mesh, either polyesteror stainless steel, which keeps the stencil foil flat and border connects the foil to the Contained Paste Transfer HeadA stencil printerhead that holds, in a single replaceable component, thesqueegee blades and a pressurized chamber filled with sol-der Etch FactorEtch Factor = Etched Depth/Lateral.

6 Etch in a chemical etching FiducialsReference marks on the stencil foil (andother board layers) for aligning the board and the stencilwhen using a vision system in a Fine-Pitch BGA/Chip Scale Package (CSP)Ballgrid array with less than 1 mm [39 mil] pitch. This is alsoknown as Chip Scale Package (CSP) when the packagesize is no more than the area of the original die *Fine-Pitch Technology (FPT)A surface-mountassembly technology with component terminations on cen-ters less than or equal to mm [ mil]. FoilThe sheet used to create the FrameThis may be made of tubular or cast alu-minum to which a tensioned mesh (border) is permanentlybonded using an adhesive. The foil is bonded to the foils can be mounted into a re-usable tensioningmaster frame and do not require a mesh border and negatea permanent bonding of the foil to the *Intrusive SolderingIntrusive soldering may alsobe known as paste-in-hole, pin-in-hole, or pin-in-paste sol-dering.

7 This is a process in which the solder paste for thethrough-hole components is applied using the stencil . Thethrough-hole components are inserted and reflow-solderedtogether with the surface-mount *LandA portion of a conductive pattern usuallyused for the connection and/or attachment of ModificationThe process of changing an aperturein size or *OverprintingThe use of stencils with apertureslarger than the lands or annular rings on the *PadSee *SqueegeeA metal or polymer blade used towipe a material (ink or solder paste) across a stencil or silkscreen to force the material through the openings in thescreen or stencil , onto the surface of a printed board ormounting structure. Normally the squeegee is mounted atan angle such that the contacting edge of the squeegeetrails behind the print head and the face of the squeegeeslopes Standard BGABall grid array with 1 mm [39mil] pitch or *StencilA thin sheet of material containing open-ings to reflect a specific pattern, designed to transfer apaste-like material to a substrate for the purpose of compo-nent Step StencilA stencil with more than one foilthickness *Surface-Mount Technology (SMT)The electri-cal connection of components to the surface of a conduc-tive pattern that does not utilize component *Through-Hole Technology (THT)The electricalconnection of components to a conductive pattern by theuse of component 2007 IPC-7525A1