IPC-CM-770D-1996.pdf - 第100页

IPC-CM-770 Januaty 1996 Power plane Metal Supporting Plane IPC-I- Figure 19-2 Sequentially-processed Structure with Supporting Plane Power distribution Leadless ceramic Wire encapsulation Metal support plane Insulating d…

January

1996

IPC-CM-770

Table

19-1

Packaging and Interconnecting Structure Comparison

ORGANIC BASE SUBSTRATE

Epoxy Fiberglass

Polyimide Fiberglass

Epoxy Aramid Fiber

Polyimide Aramid Fiber

Polyimide Quartz (Fused Silica)

Fiberglass/Aramid Composite

Fiber

Fiberglass/Teflon @Laminates

Flexible Dielectric

Thermoplastic

NON-ORGANIC BASE

Alumina (Ceramic)

SUPPORTING PLANE

Printed Board Bonded to Plane

Support (Metal or Non-metal)

Sequential Processed Board with

Supporting Plane Core

Discrete Wire

CONSTRAINING CORE

Porcelainized Copper Clad Invar

Printed Board Bonded With

Constraining Metal Core

Printed Board Bonded to Low

Expansion Graphite Fiber Core

Compliant Layer Structures

Major Advantages

Substate size, weight,

reworkable, dielectric properties,

conventional board processing.

Same as Epoxy Fiberglass plus

high temperature

axis CTE,

substrate size, weight,

reworkable, dielectric properties.

Same as Epoxy Fiberglass, X-Y

axis CTE, substrate size, lightest

weight, reworkable, dielectric

properties.

Same as Epoxy Aramid Fiber,

axis CTE, substate size, weight,

reworkable, dielectric properties.

Same as Polyimide Aramid Fiber,

axis CTE, substrate size,

weight, reworkable, dielectric

properties.

Same as Polyimide Aramid Fiber,

no surface microcracks,

axis

CTE, substrate size, weight,

reworkable, dielectric properties.

Dielectric constant, high

temperature.

Light weight, minimal concern to

CTE, configuration flexibility.

3-D configurations, low

high-volume cost.

CTE, thermal conductivity,

conventional thick film or thin film

processing, integrated resistors.

Substrate size, reworkability,

dielectric properties, conventional

board processing. X-Y axis CTE,

stiffness, shielding, cooling.

Same as board bonded to

supporting plane.

High-speed interconnections.

Good thermal and electrical

features.

Same as Alumina.

Same as board bonded to

supporting plane.

Same as board bonded to low

expansion metal cores, stiffness,

thermal conductivity, low weight.

Substrate size, dielectric

properties, X-Y axis, CTE.

Major Disadvantages

Because of its high X-Y plane Thermal conductivity, X,Y and

Comments

axis CTE. CTE. It should be limited to

environments and applications

with small changes in

temperature and/or small

packages.

Thermal conductivity, X and Y

axis CTE, moisture absorption.

Same as Epoxy Fiberglass.

Thermal conductivity, X and Y

Resin selection critical to water absorption.

controlled to tailor X-Y CTE. axis CTE, resin microcracking,

Volume fraction of fiber can be

reducing resin microcracks.

Thermal conductivity, X and Y Same as Epoxy Aramid Fiber.

axis CTE, resin microcracking,

water absorption.

Thermal conductivity, X and Y Volume fraction of fiber can be

axis CTE,

axis CTE, drilling controlled to tailor X-Y CTE. Drill

availability, cost, low resin wearout higher than with

content required.

fiberglass.

Thermal conductivity, X and Y Resin microcracks are confined

axis CTE, water absorption, to internal layers and cannot

process solution entrapment.

damage external circuitry.

Same as Epoxy Fiberglass, low Suitable for high speed logic

temperature stability, thermal applications. Same as Epoxy

conductivity. X and Y axis CTE.

Fiberglass.

Size. Rigid-flexible boards offer

High injection-molding setup Relatively new for these

trade-off compromises.

costs.

applications.

Substrate size, rework limitations,

circuit technology. weight, cost, brittle, dielectric

Most widely used for hybrid

constant.

Weight.

The thickness/CTE of the metal

core can be varied along with the

board thickness, to tailor the

overall CTE of the composite.

supporting plane.

Weight.

expansion metal support plane. special equipment.

Same as board bonded to two

Licensed process. Requires

Same as board bonded to

Reworkability, compatible thick

Same as board bonded to Weight, internal layer registration.

under development. film materials.

Thick film materials are still

supporting plane.

board can be varied to tailor the

overall CTE of the composite.

difference in CTE between

ceramic package and substrate.

Cost. The thickness of the graphite and

axis CTE, thermal conductivity. Compliant layer absorbs

4-3

Licensed by Information Handling Services

IPC-CM-770

Januaty

1996

Power

plane

Metal

Supporting Plane

IPC-I-

Figure 19-2 Sequentially-processed Structure with Supporting Plane

Power

distribution

Leadless

ceramic

Wire

encapsulation

Metal support plane

Insulating dielectric Insulated copper wire

IPC-I-

Figure 19-3 Discrete-wire Structure with Low-expansion Metal Support Plane

polyimide flexible printed wiring, as shown in Figure

19-4.

These assemblies can be constructed in multilayer form

while retaining the low-modulus feature that reduces

residual strain at the solder joints. Furthermore, lasers can

drill very fine holes in the thin printed wiring laminate.

These holes can be plated-through or filled with solid cop-

per, as required.

To retain inherent flexibility while dissipating head from

the solder joint, cutouts in the flexible circuit accommodate

pillars from the metal heatsink support plane. Although this

appears to be heavy and cumbersome, if the heatsink base-

plates are made from thin sheets of aluminum, the result-

ing density of the combined circuidheatsink assembly

might actually be less than other constructions.

19.4 Constraining Core Printed Board Structures

with supporting-plane printed board structures, one or more

supporting metallic or non-metallic planes can serve as a

stiffener, heatsink, and/or CTE constraint in constraining

core printed board structures.

19.4.1 Porcelainized-Metal (Metal Core) Structures

integral core of low-expansion metal (e.g., copper-clad

Invar), can reduce the CTE of porcelainized-metal printed

board structures

that it closely matches the CTE of the

ceramic chip carrier. Also, the printed board structure size

is virtually unlimited. However, the low melting point of

the porcelain requires low-firing-temperature conductor,

dielectric and resistor inks.

A number of composite printed board structures use lead-

less components. An integral material with a lower CTE

than that of the printed boards controls the CTE of these

structures.

19.4.2 Printed Board With Constraining (not electrically

functioning) Core

Printed boards bonded back-to-back to

a constraining core can be used for high-density, low-

warpage printed board structures. The core acts as a heat-

sink, but in this case is not electrically functional. For opti-

mum density with this approach, use a multilayer

construction with a centrally-located predrilled, low-CTE

4-32

Licensed by Information Handling Services

Januaw

1996

IPC-CM-770

Second

level Top clamp plate

heat

sink

second

level

Clamping screw

Edge

connector

Thermal

grease

Buried via

Spacar

post

IPC-I-

Figure 19-4 Flexible Printed Board with Metal Support Plane

core, (Figure

19-5).

The holes in the core are filled with a Molybdenum can be used as the core in these printed board

compatible resin prior to lamination and the printed board structures for special applications that require inherent

structure completed with conventional fabrication stiffness in extreme environments, but molybdenum and

techniques.

copper-clad Invar are difficult materials to fabricate using

Dielectric

Circuit lines

Supportingare

IPC-I-

Figure 19-5 Printed Board with Supporting Plane (Not Electrically-functional Constraining Core)

4-33

Licensed by Information Handling Services