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IPC - IPC Standard - IPC-4121
IPC-4121 :

Guidelines for Selecting Core Constructions for Multilayer Printed Wiring Board Applications

File Format PDF  
Price $35  
Rev 2000    
Language English    
Number of page 20  
Date of Publication 2000  


This specification defines guidelines for selecting core constructions in terms of fiberglass fabric style and configuration for use in multilayer PWB applications. Each core construction is given a registration number for ordering purposes. Every effort shall be made to periodically review the construction guideline and include or exclude constructions based on current data. 


This document groups the core constructions into categories based on relative nominal thickness. Within a nominal thickness category, the different core constructions are characterized in terms of resin content, dielectric thickness, glass transition temperature (Tg), availability, and cost. The core constructions are also compared for performance attributes, including machinability, dimensional stability, Z-axis expansion, measle resistance, chemical resistance, and flatness. 


Resin System 

The guideline to registered core constructions is applicable only to laminates as referenced in the appropriate slash sheet. 

Slash Sheet 1 Laminates comprised of a majority of difunctional epoxy resin with a Tg of 110°C to 150°C [230°F to 302°F] (IPC-4101/21). 

Slash Sheet 2 Laminates comprised of a modified difunctional epoxy resin with a Tg range of 150°C to 200°C [302°F to 392°F] (IPC-4101/23, IPC-4101/24, and IPC-4101/26). 

Slash Sheet 3 Laminates comprised of a majority of cyanate ester resin with a Tg range of 170°C to 220°C [338°F to 428°F] (IPC-4101/30). 

Slash Sheet 4 Laminates comprised of a bismalemide triazine resin with a Tg range of 170°C to 230°C [338°F to 446°F] (IPC-4101/71). 

Slash Sheet 5 Laminates comprised of a majority polyimide resin with a minimum Tg of 200°C [392°F] (IPC-4101/40, IPC-4101/41, and IPC-4101/42). 


The guideline to registered core constructions is applicable only to laminates comprised of woven "E" glass fabrics of plain weave as documented in IPC-4412. 

Fabric Interchangeability 

This guideline only references glass style 2313. Glass styles 2113 and 3313 may be used as substitutes for 2313 in each construction shown. 

Alternate Constructions For each thickness category, other possibilities for constructions may exist and be manufactured commercially. The constructions indicated in the construction selection guide have been chosen based on the consensus of industry experts (both laminate suppliers and PWB fabricators). Alternate constructions may be found that perform better than those listed in the guideline for specific applications and may be used upon agreement between user and supplier. 

Grading System 

The grading system of the slash sheets are numbered 1 through 5, with each number indicating the relative performance between constructions for a particular property or characteristic. The following are the slash sheet core construction indicators. 

1 Core constructions with the most applicable performance. 

2 Core constructions with better than intermediate levels of performance. 

3 Core constructions with intermediate levels of performance. 

4 Core constructions with less than intermediate levels of performance. 

5 Core constructions with the least applicable performance.

IPC-A-610  IPC-A-600 IPC-A-620 IPC-7711/7721