Guidance for strain gage limits for printed circuit assemblies

Pdf a novel flexible strain gauge sensor fabricated using. Pcb testing services printed circuit boards are often exposed to. Since strain is relative to location, the same strain gage location must be used for testing as was used to get the strain guidance. Strain gages have a characteristic gage factor, defined as the fractional change in resistance divided by the strain. Strain gage construction most strain gages are of foil construction, illustrated in fig. This document is meant to be used as a methodology for strain gage placement and subsequent testing of printed circuit assemblies pcas using strain gages. Guidance for strain gage limits for printed circuit assemblies 1 scope this document describes specific guidance for strain gage limits for printed circuit assemblies pcas in the printed board. Ipc jedec9704a printed circuit board electrical engineering. The challenge is in finding and setting the strain limits so that your design and component set are not jeopardized by elevated micro strain levels. This resistance may change only a fraction of a percent for the full force range of the gauge, given the limitations imposed by the elastic limits of the gauge material and of the test specimen. Address the importance of using a consistent strain gage placement along package diagonal to properly assess risk update the document to reflect new pwb strain guidance related to pbfree technology discuss and incorporate best practices from experienced ipcjedec9704 users update appendix a strain limits of ipcjedec9704 to. Strain gage in this laboratory we design our first electronic device, an electronic weight scale.

First, the printed circuit board must be prepared for the installation of a strain gauge. Printed circuit assembly strain gage test guideline 1 scope this document is meant to be used as a methodology for strain gage placement and subsequent testing of printed circuit assemblies pcas. Strain gage limits for pcb assemblies printed circuit board. Ipcwp011, guidance for strain gage limits for printed circuit assemblies, association connecting electronics industries, 2011. Printed circuit assemblies as stress analysts we have repetitive tasks to complete in the lab, field or on the production floor. Applying strain levels that are beyond the capability of the strain gage or bonding adhesive 9. The board level assembly technology which contains. Ipcwp011 guidance for strain gage limits for printed circuit assemblies.

Unless the gages are placed in the same location, strain numbers cannot be compared to the strain guidance. With a few assumptions and simplifications, the following equation can be determined further explanations are given in the hbm book an introduction to measurements using strain gauges. Applying strain levels that produce yield in the structure produces a zero shift in the strain gages 8. Selecting the proper amplifier for straingauge applications. Buy ipc a printed circuit assembly strain gage test guideline from sai global. Document provides overview of board flexure control methodology, board preparation, intelr bfi metrics. Preparation of a pcb for the installation of a foil strain gauge. We will also use an instrumentation amplifier to gain up the signal.

Strain gauges have an electrical path whose resistivity. Since the foil used in a strain gage must be very fine or thin to have a sufficiently. Microstrain is a dimensionless value labeled microstrain strain, e. Select the gage series for the temperature range consider the temperature range that will be encountered during the strain measurements and select a gage series that meets your requirements. Consider the temperature range that will be encountered during the strain measurements and select a gage series that meets your requirements. In the applicable assembly steps, diagonal strain guidance should be. Failures of multilayer ceramic capacitors mlccs caused by printed circuit board pcb flexure have received considerable attention recently, not only because of product reliability concerns, but also. The ipc jedec9704 guideline identifies problematic assembly and test. Ensure the vent hole lines up directly below the sensors gage hole and.

Sti analytical lab has taken a lead role in strain gage testing and data evaluation of applied strain and strain rate on printed circuit card assemblies. The key component is a strain gage, a resistor that changes its value in response to mechanical stress. Figure 1 shows a strain gage with two electrical leads on the right side. How to measure strain rate on printed circuit boards pcbs hbm. Strain gage resistance the resistance of a strain gage is defined as the electrical resistance measured between. Polymer strain gage, pdms printed strain gage, printed. Strain gages for measuring strain and stress on a pcb. Pca strain measurement includes application of strain gages to the printed board near speci. Experimental determination of strain distribution on printed. Intel strain measurement methodology for circuit board assembly download pdf guide. Failures of multilayer ceramic capacitors mlccs caused by printed circuit board pcb flexure have received considerable attention recently, not only because of product reliability concerns, but also because there is no screening method available for detecting cracked capacitors after they are assembled onto circuit boards. Please first verify your email before subscribing to alerts.

Temperature response of strain gage installations 5. The suggested procedures enables board manufacturers to conduct required strain. Evaluation of structural design methodologies for predicting. Strain gages for measuring strain and stress on a pcb kyowa. Pros and cons of common strain gage wire materials constantan advance, copel alloy is the oldest and most widely used strain gage materials it has a high enough electric resistivity r 0. Intel strain measurement methodology for circuit board assembly. The idea is that the maximum principal strain yaxis should not exceed a certain value. Document provides overview of board flexure control methodology, board preparation, intelr bfi metrics, component determinations, with motherboard assembly line strain measurement, flexure reductions, test planning, and general procedures. Select the gage series for the temperature range consider the temperature range that will be encountered during the strain. Strain and strain rate measurement on printed circuit boards. For interpreting strain according to the experimentally determined guidelines published in ipc 9704a, triaxial gauges are necessary. The allowable strain levels, for instance, are provided in ipcwp011, titled guidance for strain gage limits for printed circuit assembliesrate limited, but our client may have their own allowable limits. The allowable strain levels, for instance, are provided in ipcwp011, titled guidance for strain gage limits for printed circuit assembliesrate limited, but our client may have their own allowable limits as well that they have derived through testing of their product.

The strain gauge tests of printed circuit boards pcb represents complex work including fea. The following graph from ipcjedec9704a printed circuit assembly strain gage test guideline displays where the maximum allowable safe pwb. Sti analytical lab has taken a lead role in strain gage. Pressure sensor surface mount smt guidelines technical. This presentation will not explain the math used for predicting strain. Our new checklist is simply a standardized list of 8 required steps developed for a repetitive strain measurement task on a pcb. Intel strain measurement methodology for circuit board. The device is still being used in many electronic circuits mainly as the principle sensing element for sensors like torque sensors, pressure. A highly stable measurement circuit, regulated bridge excitation supply, and precisely. Our new pdms polymer strain gage is a compact and costeffective solution for detecting and measuring pressure. Ipc, guidance for strain gage limits for printed circuit assemblies, 2011. Whenever there are modifications to an assembly process that might alter the strain profile. Strain gage rosettes on pcb for testing solder ball joint strains as per.

For example, 2 microstrain applied to a gage with gage factor of 2 produces a fractional resistance change of 2x210 6 4x10 6, or 4 w. The carrier, dimensions are designed by omega for the optimum function of the strain gage. Often we find that if we dont have any guidance, we may forget certain steps in a process. The method describes specific guidelines for strain gage testing of pcas during the printed board manufacturing process, including assembly, test, system integration, and other types of. A wheatstone bridge for a straingauge application consists.

Printed circuit assembly strain gage test guideline. To picture the limit line, define the following data series function. Ipcjedec9704 6 guideline document recommends using threeelement stacked rosette strain gages for pcb strain. The device was invented in the year 1938 by edward e. Buy ipc a printed circuit assembly strain gage test. Straingage construction most strain gages are of foil construction, illustrated in fig. Strain gage install on printed circuit boards pcb youtube. Strain gages are attached to printed circuit boards in order to relate strain. For example, 2 microstrain applied to a gage with gage factor of 2 produces a fractional. Strain gage installation checklist printed circuit assemblies step 3a. Still symbols normal stress shear stress strain normal microstrain x 10 6 shear strain e modulus of elasticity or youngs modulus poisson ratio gf gage factor rg gage. A strain gauge is a device that is used to measure the strain that occurs in an object. Pressure sensor surface mount smt guidelines technical note. Even though, there are reports on the fabrication of strain gauges on glass substrates 22, printed circuit boards 23 and polyethylene terephthalate substrates 24 using screen, inkjet and.

Applying strain gages to bolted assemblies bolted joints typically slip during loading, resulting in the strain gages poor return to zero. Coping with the risk of board flexure damage to multilayer. Typically, one or more strain gauges are arranged in a wheatstonebridge configuration, due to the excellent sensitivity that this circuit offers. Measure strain on a pcb during mounting, cutting, assembling, ets. Whenever there are modifications to a test fixture that might alter the strain profile. Strain gauge electronic circuits and diagramselectronic. Foil strain gages are usually made by a printed circuit process.

Strain gage placement for intel bga components plan of record location and alternate gage locations. Guidance for strain gage limits for printed circuit assemblies. Printed circuit assembly strain gauge test guideline. Buy ipc a printed circuit assembly strain gage test guideline. General test methods for materials and assemblies guidance. More than 2,000 different types of strain gauges available for nearly any measurement task. The effectiveness of the proposed structural design methodologies was evaluated by comparing the margin of safety calculated from various analysis approaches and the random vibration fatigue. Principal strain peak value strain rate time history test frequency before any test or assembly fixture is brought online. Ensure appropriate surface preparation materials are on hand. For strain measurements, the resistances r 1 and r 2 must be equal in the wheatstone bridge.

Make a formal strain report comparing maximum diagonal strain. For directattach bga components, the center of the strain gages must be at the intersection of lines 0. With a few assumptions and simplifications, the following equation can be. Board strain can be identified and measured through tools such as. Guidance for strain gage limits for printed circuit. Ipcjedec9704a printed circuit assembly strain gage test guideline. For interpreting strain according to the experimentally. How to measure strain rate on printed circuit boards pcbs. Printed circuit assembly strain gage test guideline 1 scope this document is meant to be used as a methodology for strain gage placement and subsequent testing of printed circuit assemblies pcas using strain gages. Address the importance of using a consistent strain gage placement along package diagonal to properly assess risk update the document to reflect new pwb strain guidance related to pbfree.

Experimental validation of fatigue life of ccga 624 package. January printed circuit assembly strain gage test guideline supersedes ipcjedeca june a standard developed by. Strain age installation checlist printed circuit assemblies. Electronic function materials, in liquid or paste form, are printed. To perform a test to measure strain in an electronics application, small body size gauges, with bi or triaxial configurations are mounted to a pcb. Due to screw assemblies, the surface level differences on which the pcb is placed. Aug 09, 2017 this micromeasurements inotes video shows correct installation of precabled strain gage sometimes spelled gauge rosettes on a printed circuit board pcb in preparation for testing. Ipcjedec a printed circuit assembly board strain gage test guidelines. They outline strain limits and provide reference for rate limited strain guidance for eutectic solder. Printed wiring board strain gage test guideline, the measured strain is. Identify and characterize damaging pcb assembly and test. Experimental determination of strain distribution on printed circuit boards using digital image correlation.