Design

Company Overview

Advanced Technical Ceramics Company (AdTech Ceramics) is located in Chattanooga, Tennessee.

Founded with a proven employee base and manufacturing capability for multilayer co-fired electronic packages
Processes revolve around 30 plus years of experience in material science, engineering, design, tooling and
manufacturing of multilayer ceramics
Materials include Alumina (HTCC), Aluminum Nitride, BeO and LTCC
Chemical Milling services available (step lids, leads, seal rings) in Kovar, Alloy 42, Spring Steel and Stainless Steel
Market emphasis targets engineering solutions for high reliability applications
Business model focuses on long term stability and growth
Manufacturing capabilities include prototype to high volume production
US owned, US based, ITAR Compliant
MIL-1-45208
ISO 9001:2000 Certified.

AdTech Ceramics continues to drive process, facility and equipment improvements and advancements, and actively
seeks new opportunities in advanced Note: These general guidelines should be used for typical designs. If
exceptions or special requirements are needed they should be reviewed with AdTech Ceramics.

Advanced Technical Ceramics Company
511 Manufacturers Road
Chattanooga, Tennessee 37405
(423) 755-5400
(423) 755-5438 Fax
Internet: www.AdTechCeramics.com
Email: sales@AdTechCeramics.com

Product Capabilities Include

Custom Advanced Packages, Multichip Modules, Substrates and Packages, Microwave Packages

High Frequency Feed Throughs, Power Dissipation Packages, Optical Packages High Lead Count Packages

Custom Pin Grid Arrays, Sensor Packages, Crystal/Oscillator/SAW Packages

Pad Array Carriers (Ball Grid Arrays), Ceramic/Metal Packages, Chemical Milling

Process Overview

Electronic packages produced with the co-fire multilayer ceramic process have four distinct processing stages:

Materials Preparation
Green Processing
Sintering
Post-fire Processing

Materials Preparation

Ceramic materials are prepared by milling precise amounts of raw materials into a homogeneous slurry. This mixture
is principally ceramic powders of controlled particle sizes with fluxes and small amounts of organic binders and solvents.
This slurry is poured onto a carrier and then passed under a blade to produce a uniform strip of specific thickness. When
dried, this strip becomes a ceramic-filled “tape” which is easily handled in rolls or sheets for unfired processing. Metal
powders of exact compositions and particle sizes are prepared as “pastes” for subsequent screen printing on the green
ceramic tape, or in some cases, on the fired ceramic. Likewise, ceramic powders can be prepared as pastes to be used
as screen printed dielectric layers.

Green Processing

Except for very large or complex products, individual products are arranged in arrays for multiple processing. Via holes,
edge castellations and cavities are then punched in the tape. Because of the abrasive nature of ceramics, special tooling
must be used for these operations. Green processing of ceramic is very sensitive to particulates and is done in a Class
10,000 Clean Room.

Via holes are filled with a refractory metal paste, or bore coated, to become the vertical electrical interconnections between
the layers. Conductive circuit patterns are printed onto the ceramic tape with refractory metal pastes using precision screen
printing.

The layers are then stacked and laminated together. At this point the array may be scored to allow post fire operations
in the array, or individual products may be cut or punched out of the array prior to sintering.

Sintering (Firing)

The ceramic-refractory metal composite structure is sintered, or “co-fired,” at temperatures as high as 1600°C in a carefully
controlled atmosphere. During the firing process most ceramics shrink approximately 20% in the X, Y and Z dimension.
Hot pressed AlN is physically constrained in the X and Y dimensions so that all shrinkage occurs in the Z dimension.

Post Fire Processing

Ceramic packages are typically supplied with Gold over Nickel plating on the metallized areas, and can have metal
components attached by brazing. Nickel is plated on all exposed metal surfaces to allow brazing and to provide solderability.
Metal leads, pins, seal rings and heat sinks are attached by brazing with silver or a silver-copper eutectic alloy to form
a strong hermetic joint. Final plating may be either electroless or electrolytic gold. Electrolytic plating requires that all
exposed circuits be temporarily electrically connected through a lead frame, internal tie bar, or a combination of the two.
A combination of electrolytic and electroless plating can be used if designs require. (Note: in this case metal components
must be electrolytic.) Post fire metallizations can be used for applications requiring special flatness or precision tolerances.
Ceramic grinding, lapping and ultrasonic machining are available for applications requiring features not achievable as-fired.

Co-fire Multilayer
Ceramic Process

Structural & Interconnect Design Guidelines

Printer Friendly Version Structural Parameters | Vertical Interconnects | Horizontal Interconnects | Detailed PDF Version

Design considerations for multilayer ceramic packages can be grouped into these categories:

Structural Parameters
Interconnect Layout
Special Features

Structural Parameters

Each ceramic material has specific design and tolerance limitations due to their physical properties and processing
technologies. These include size, number of layers, and flatness.

Features	Description	Alumina	Aluminum Nitride
Length/Width (X/Y)	Standard Tolerances	±1% NLT ±0.13mm ±(.005")	±.005"
	Special Tolerances	±.5%	(Sawed) ± 0.05mm (.002")
Layer Thickness (A)	Standard	0.18mm (.007") to 0.64mm (.025")	0.13mm (.005")
	Special	0.13mm (.005") to 0.76mm (.030")	0.09mm (.0035") to 0.38mm (.015")
	Standard Tolerances	±10%	±10%
	Special Tolerances	±5%	n/a
Package Thickness (Z)	Range	0.25mm (.010") - 8.89mm (.350")	3.4mm (0.135")max
	Standard Tolerances	±10%	±0.08mm (.003")
	Special Tolerances	±5%	±0.03mm (.001")
Flatness	Standard	0.08mm/mm (.003"/inch)	0.03mm/mm (.001")/inch
	Special (Machined)	0.03mm/mm (.001"/inch)	n/a
Surface Finish	As Fired	<1.14µm (45µ")	n/a
	Lapped	<0.51µm (20µ")	<0.64µm(25µ")
	Polished	n/a	<0.13µm(5µ")

Vertical Interconnects

The basic interconnect between layers is the metal-filled via. Also used are bore coated (metallized side wall) vias,
metallized edge castellations and flat edge metallization. Generally, via diameters should be at least the thickness of
the ceramic layer and via pitch 2.5 times the layer thickness. Vias may require a cover pad to be printed with the metal
interconnect pattern to assure optimal electrical connection between layers.

Feature	Description	Alumina	Aluminum Nitride
Filled Via (B)	Diameter Range	0.10mm (.004") - 0.51mm (.020")	0.13mm (.005") - 0.51mm (.020")
(C)	Cover Pad dia (Internal)	Via dia + 0.05mm (.002")	Via DIA+0.05mm (.002")
(C)	Cover Pad dia (External)	Via dia + 0.13mm (.005")	Via DIA+0.38mm (.015")*
(D)	Via-to-Via Centerline	0.30mm (.012") Min.	0.38mm (.015") Min.
(R)	Via-to-Edge (Standard)	w = t + v (web = thickness + via diameter)	0.25mm (.010")
	Via-to-Edge (Sawed Edge)	0.20mm (.008") Internal Via	0.20mm (.008") Internal Via
	Via-to-Edge (Sawed Edge)	0.00 Split Via (see page 10)	n/a
Bore Coated Via (Q)	Diameter Range	0.30mm (.012") - 0.64mm (.025")	n/a
	Cover Pad Diameter	Hole dia + 0.25mm (.010")	n/a
(P)	Castellation Radius (Typical)	0.20mm (.008")	n/a
Edge Metallization (L)	Centerline	0.64mm (.025")Min.	n/a
(J)	Circuit Neckdown (Range)	0.13mm (.005") to Width of Edge Metal	n/a
(K)	Pullback From Edge	0.51mm (.020") (TYP) 0.25mm (.010") Min.	n/a

Horizontal Interconnects

Circuit layout is usually a compromise between maximizing conductor trace width to minimize resistance, and maximizing
the space between conductors, and other metal features such as vias, in order to minimize yield losses. It is desirable to pull
back buried metal features from the ceramic edge, and neck down conductors that terminate with edge metallization. Internal
ground planes should be limited to a maximum of 75% metal coverage.

Feature	Description	Alumina	Aluminum Nitride (AIN)
Internal Metal Circuit (F)	Typical Width	0.15mm (.006") - 0.25mm (.010")	0.15mm (.006”) - 0.25mm (.010")
	Custom Width	0.10mm (.004")	0.10mm (.004")
(G)	Typical Space	0.15mm (.006") - 0.25mm (.010")	0.15mm (.006”) - 0.25mm (.010")
	Custom Space	0.13mm (.005")	0.13mm (.005")
	Maximum Coverage	85%	75%
	Recommended Grid	Equal lines and spaces	Equal lines and spaces
(I)	Typical Space from Edge	0.76mm (.030")	0.254mm (.010")
	Custom Space from Edge (Sawed)	0.13mm (.005")	0.20mm (.008")
Surface Metal Circuit (F)	Typical Width	0.20mm (.008")	0.20mm (.008")*
	Custom Width	0.10mm (.004")	0.10mm (.004")*
(G)	Typical Space	0.20mm (.008")	0.20mm (.008")*
	Custom Space	0.13mm (.005")	0.10mm (.004")*
	Maximum Coverage	100%	100%
(E)	Typical Space from Edge	0.25mm (.010")	0.254mm (.010")*
	Custom Space from Edge	0.00mm (.000")	0.18mm (.007")*
Relation to Vias (M)	Isolation Ring Around Cover Pad	0.38mm (.015")	0.20mm (.008")*
	Custom Isolation Ring	0.25mm (.010")	0.10mm (.004")*
(N)	Circuit to Cover Pad	0.25mm (.010")	0.20mm (.008")*
	Custom Space (External)	0.15mm (.006")	0.10mm (.004")*
	Custom Space (Internal)	0.20mm (.008")	0.20mm (.008")*

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Special Feature Design Guidelines
Special consideration should be given to the design of the following features:

Cavities
Wire Bond Pads
Metal Components
Special Enhancements or Finishes

Cavities
Cavities are punched into the ceramic in its green state. Metallization should generally be pulled back from the edges of
cavities. When cavity floors are metallized, the metallization should extend beyond the cavity wall to assure complete
coverage.

Wire Bond Pad Design
By designing wire bond pads in a radial pattern (from the center of the cavity) it is possible to compensate for variations
in the co-fired shrinkage. For very high density applications wire bond pads can be staggered in a double row around
the die, achieving pads as small as 0.15mm (.006") x 0.15mm (.006") on an effective 0.15mm (.006" )pitch.

Cavity Design

Feature	Description	Alumina	Aluminum Nitride*
Die Attach Pad (A)	Typical Extension	0.51mm (.020")	N/A
	Minimum Extension	0.25m