1 association CONNECTINGELECTRONICS INDUSTRIES IPC- 4761 Design Guidefor Protectionof Printed BoardVia StructuresDeveloped by the Via Protection Task Group (D-33d)of the Rigid Printed Board Committee (D-30) of IPCU sers of this publication are encouraged to participate in thedevelopment of future :IPC3000 Lakeside Drive, Suite 309 SBannockburn, Illinois60015-1219 Tel 847 847 Contents1 and 12 APPLICABLE .. 13 PWB FABRICATION AND of Via Fabrication or Plug Separation from Plated HoleWall .. Process Term Reliability 44 MATERIALS/DESIGN Use of Materials for (Organic) Non-imageable .. for Tented/Covered Via Structures .. and Specification and 65 VIA PROTECTION DEFINITIONS AND Via (Type I Via).
2 And Covered Via (Type II Via).. Via (Type III Via).. and Covered Via (Type IV Via).. Via (Type V Via).. and Covered Via (Type VI Via).. and Capped Via (Type VII Via).. Filled 106 PERFORMANCE of Conformal 117 SAMPLE 118 EXAMPLES OF DRAWING 12 FiguresFigure 1-1 Bumped Via Protection 1 Figure 1-2 Dimpled Via Protection 1 Figure 1-3 Planarized and Capped Via 1 Figure 3-1 Example of Hole Fill/Plug Separation fromPlated Hole 3 Figure 3-2 Example of Depression Within 3 Figure 3-3 Voids in Via Fill 3 Figure 3-4 Large Voids in Via Fill 3 Figure 3-5 Corroding of Hole Wall Plating Resulting fromSingle-Side Via 4 Figure 5-1 Examples of Type I Tented 6 Figure 5-2 Examples of Type II Tented and 7 Figure 5-3 Examples of Type III Plugged 8 Figure 5-4 Examples of Type IV Plugged and 8 Figure 5-5 Example of Type V Filled 9 Figure 5-6 Examples of Type VI Filled and Covered Vias.
3 Dry Film 9 Figure 5-7 Examples of Type VI Filled and Covered Vias,Liquid Film 9 Figure 5-8 Examples of Type VII Filled and 10 Figure 5-9 Examples of Partially Filled 10 Figure 7-1 Illustration of Tented and Covered ViaProtection 11 Figure 7-2 Design Rule formula with exploded view oftent and cover 11 Figure 7-3 Top View Illustration of Solder MaskClearance around a BGA 12 Figure 7-4 Top View Illustration of Overlap Detail forTent and Covered 12 TablesTable 5-1 Application Guidelines for Via 6 IPC- 4761 July 2006ivDesign Guide for Protectionof Printed Board Via Structures1 SCOPEThe protection of through vias within Printed Wiring Boards(PWB) has evolved from limited use to common has evolved where via fabrication techniquesand protection methodologies need to be defined to allowcurrent designs to be manufacturable at an acceptable yieldand cost.
4 Numerous techniques and objectives exist, and willbe discussed in this document. This document is the productof the IPC D-33d Via Protection Task Group and has beendeveloped to provide guidance for the designer and fabri-cator on how via protection should be approached as well asguidance on how via protection should be specified in pro-curement PurposeThis guideline provides PWB designers,fabricators and/or users with information on existing meth-ods for the protection of vias on printed boards. In additionto detailing some of the advantages of via protection, pro-duction and material issues are given to aid the user in evalu-ating the benefits and concerns for each type of Terms and DefinitionsThe definition of all termsused hereinshallbe as specified in IPC-T-50 and as Via Protection Via protection where the holeplugging or fill material protrudes above the surface of thehole interface producing a convex shape.
5 See Figure Via Protection Via protection where the holeplugging or fill material recedes below the hole interfaceproducing a concave shape. See Figure Via Protection Via protection where the ex-cess hole plugging or fill material protruding above the holeinterface has been removed by a process to produce a co-planar surface. See Figure APPLICABLE IPC1 IPC-T-50 Terms and Definitions for Interconnecting andPackaging electronic CircuitsIPC-A-600 Acceptability of Printed BoardsIPC-SM-840 Qualification and Performance of PermanentSolder 1-1 Bumped Via Protection MaterialIPC- 4761 -1-2 Figure 1-2 Dimpled Via Protection MaterialIPC- 4761 -1-3 Figure 1-3 Planarized and Capped Via Protection MaterialJuly 2006 IPC-47611