IPC-TM-650 High Speed/High Frequency Test …

1 SummaryThis method is intended for the rapid mea-surement of the X-band ( to GHz) apparent relativestripline permittivity (see ) and loss tangent of metal cladsubstrates. Measurements are made under stripline condi-tions using a resonant element pattern card, which is sepa-rated from the ground planes by sheets of the material to betested. Further information about this method may be found inASTM DefinitionsTerms used in this method include:Complex Relative PermittivityThe values for relative per-mittivity and dissipation factor considered as a complex constant (see IPC-T-50) or relative per-mittivity. The symbol used in this document is or aresometimes PermittivityA dimensionless ratio of absolute per-mittivity of a dielectric to the absolute permittivity of a TangentDissipation factor (see IPC-T-50), dielectricloss tangent.

2 The symbol used in this document is tan ( ). LimitationsThe following limitations in the methodshould be noted. Users are cautioned against assuming themethod yields permittivity and loss tangent values that directlycorrespond to applications. The value of the method is forassuring consistency of product, thus reproducibility of resultsin fabricated measured effective permittivity for the resonatorelement can differ from that observed in an the application is in stripline and the line width togroundplane spacing is less than that of the resonator ele-ment in the test, the application will exhibit a greater compo-nent of the electric field in the X, Y plane.

3 Heterogeneousdielectric composites are anisotropic to some degree, result-ing in a higher observed rfor narrower lines in an application may also differ from the testin the fraction of substrate electric field component in the X, stripline assemblies have air excluded betweenboards, thus tend to show greater degrees of anisotropy of some composites canresult in an increased degree of coupling of the resonant ele-ment, resulting in a falsely lower Q value. If a correction is notapplied either mathematically as in or by deviating fromthe probe gaps specified for the test pattern, an upward biasin the calculated loss tangent will sensitivity of the method to differences in rofspecimens is impaired by the fact that the resonator patterncard remains as part of the fixture and at the same time con-stitutes a significant part of the dielectric involved in method does not lend itself to use of stable ref-eree specimens of known electric properties traceable to TheNational Institute of Standards and Technology (NIST).

4 Applicable IPCIPC-T-50 Terms and DefinitionsIPC-MF-150 Metal foil for Printed Wiring ApplicationIPC-TM-650 Method , Cupric Chloride EtchingIPC-TM-650 Method , Permittivity (Dielectric Con-stant) and Loss Tangent (Dissipation Factor) of Materials (TwoFluid Cell Method)ASTM D3380-75 Standard Method of Test for Permittivity(Dielectric Constant) and Dissipation Factor of Plastic-BasedMicrowave Circuit Test SpecimenAll metal cladding shall be removedfrom the material to be tested by any standard etching pro-cess, including rinsing and drying; however, IPC-TM-650 ,Method , shall be used as a referee procedure. Thetest specimen shall consist of a set of two sheets (or twopackets of sheets) of a preferred size of at least 51 mm x smaller size may be used if it has been shown not toaffect results.

5 The minimum vertical dimension must extend2215 Sanders RoadNorthbrook, IL 60062-6135 IPC-TM-650 TEST methods Test for Permittivity and Loss Tangent(Dielectric Constant and Dissipation Factor) at X-BandDate3/98 RevisionCOriginating Task GroupHigh Speed/High Frequency Test MethodsSubcommittee (D-24)Material in this Test methods Manual was voluntarily established by Technical Committees of the IPC. This material is advisory onlyand its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of thismaterial. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent referenced is for the convenience of the user and does not imply endorsement by the CONNECTINGELECTRONICS INDUSTRIES from the base boards to the top of the mm x 51 mm areato which clamping pressure is applied.

6 The minimum horizon-tal dimension must be enough to extend at least mmbeyond the center line of the vertical portion of the probe lineon either side. For the pattern card of Figure 4 and fixture ofFigure 12, these minimums are mm x mm. For thesmaller size, the clamp force in or Table 1 is not changedbecause the effective area over which the force is applied isnot reduced. The test fixture is designed to accommodate atotal specimen thickness of either mm mm mm mm from an even number of :Testing of built-up specimens introduces error, whichcan exceed 5% due to air gaps. Exact correlation factors andtechniques must be agreed upon or other methods of testused.

7 The 1 MHz method of IPC-TM-650 , Method ,can be used with a correction factor based on tests ofsamples of the nominal thickness of Table 1 using both some material types not based on woven fabric rein-forcement, it is possible to machine specimens to achieve thenominal thickness for Suggested Electronic ApparatusThe principal com-ponents required for the test setup consist of the test fixturedescribed in , a microwave signal source, an accuratemeans of measuring the signal Frequency , an accurate meansfor detecting power level, and an accurate method of deter-mining Frequency values above and below the resonant fre-quency at the half-power level for the test fixture loaded withthe microwave signal source must be capable of providing anaccurate signal.

8 During the required time period and range offrequency needed to make a permittivity and loss tangentmeasurement, the source must provide a leveled power out-put that falls within a dB range. When the source is set fora particular Frequency , the output must be capable of remain-ing within 5 MHz of the set value for the time required to makea means for measuring Frequency shall have a resolution of5 MHz or less and an accuracy of 8 MHz or less. An error of+8 MHz in measurement of a resonant Frequency for a mate-rial with nominal permittivity of represents a errorin means for detecting the power level shall have a resolu-tion of dB or less and be capable of comparing powerlevels withina3dBrange with an accuracy of dB.

9 An errorof dB in estimating half power Frequency points can resultin an error in the loss tangent of about for a materialwith permittivity. See , equation Manual Test SetupThe method of determining thehalf-power points depends partly on the type of signal sourceused. If the power input to the test fixture is maintained con-stant as the Frequency is varied, then an SWR meter may beused to determine the half-power points at the output of thetest fixture. This may be accomplished by using a leveledsweep generator or by using a tunable klystron (at a consid-erable savings) and manually adjusting the power input to thetest fixture to a prescribed level by use of a variable attenua-tor.

10 A typical equipment list is shown below. Equivalent makesand models of equipment may be substituted where it can beshown that equivalent results are obtained. For example, if aleveling system is not used and the power output of thesource varies widely with Frequency , a ratiometer may be sub-stituted for the two SWR meters. If only permittivity is desired,it is not necessary to level the following equipment, or equivalent, may be used. Sweep Frequency Generator 8350B or 8620C X-Band Frequency Plug in Unit 83545A or 86251A Frequency Meter X532B Crystal Detector (2) 423B (Neg) Matched Load Resistor for one Crystal Detector , opt.