Component Palladium Lead Finish - Specification Approved by Executive Board 1997-xx-xx August 22 Version Appendices 1. User Commitment Form 2. Supplier Compliance Form Table of contents 1. Background 2. The Objectives of the Specification 3. The Scope of the Specification 4. Demonstration of Compliance with the Palladium Specification 5. Solder Joints to Leads with Palladium Finish 6. Definition of the Test Vehicle and the Soldering Process 6.1 The Test Vehicle 6.1.1 The Printed Wiring Board 6.1.2 The IC Packages 6.2 The Soldering Process 7. Properties 7.1 Properties of the Palladium Finish 7.1.1 The Ductility of the Palladium Finish 7.1.2 The Porosity of the Palladium Finish 7.1.3 Thickness of the Palladium Finish 7.1.4 Solderability of the Palladium Finish 7.1.5 Shelf life of the Palladium Finish 7.2 Properties of Solder Joints to Leads with Palladium Finish 7.2.1 Visual Appearance 7.2.2 Destructive Testing 7.2.2.1 Pull Forces at Fracture 7.2.2.2 Analysis of the Fracture Area 7.2.3 Fatigue of Solder Joints with Palladium Finish 8. Definitions 1
1 Background Component suppliers are switching over from SnPb (tin/lead) to NiPd (palladium) as component lead finish to gain cost benefits of simplified IC package assembly. Many commodity IC components have already leads with palladium finish. Test procedures and conditions for user acceptance need to be adjusted to reflect different failure mechanisms of solder joints to component leads with palladium finish compared to tin/lead finish. Palladium finish has lower environmental loading than the conventional tin/lead finish, due to absence of lead, which is an advantage. 2 The Objectives of the Specification Component leads with palladium finish have been around for some time. The objective of this specification is to define a quality specification for component leads with palladium finish. The specification is based on qualification requirements currently used by user members of HDP User Group International Inc. The requirements are applicable to both currently available and future concepts. This means that new suppliers of components with palladium lead finish shall meet the same requirements as for those already accepted by users. The specification is aimed at defining compatible qualification efforts on both the user (system supplier) and the supplier (component supplier) side reducing the efforts necessary on both sides. 3 The Scope of the Specification The specification applies to surface mounted component leads with palladium finish attached to printed wiring boards by a reflow soldering process. Through mount technology is not addressed. A test vehicle and parameters of a reflow soldering process to be used for conducting reproducible solderability and reliability tests are defined. Socketing for burn in and test is not addressed. A test plan defines the tests needed to get the specified quality. 4 Demonstration of Compliance with the Palladium Specification This palladium component lead finish specification is of value only if applied by users and suppliers. The compliance with this specification shall be demonstrated by presenting information in standardized form according to appendices 1 and 2. Commitments: Users commit to accept components with palladium from a reliability point of data according to form appendix 1 compliant with this specification Suppliers commit to deliver component leads compliant with this specification by presenting reliability data according to form appendix 2 compliant with this specification 2
The forms will facilitate an efficient communication between users and suppliers. 5 Solder Joints to Leads with Palladium Finish The palladium finish is considered as a sacrificial layer provided to protect the underlying ductile nickel finish from oxidation. The finish is applied to the base metal lead frame consisting of either nickel-iron or copper alloy. The solder joint is formed between the tin-based solder alloy and the underlying nickel plating. A good solder joint can be identified by: Visual inspection Measurement of pull forces at fracture. Determination of the exact location of the fracture Analysis of the fracture area between component lead and solder surface. The pull forces at fracture shall reach certain minimum values. The fracture region (between component lead and pad on the printed wiring board) shall be porous. The fracture shall take place in the solder rather than in the interface area between pin and solder. The visual appearance of the solder joints to palladium finished component leads differs from the appearance of leads having tin/lead finish. The results of the visual inspection are only partly in coincidence with the quality of the solder joints. 6 Definition of the Test Vehicle and the Soldering Process The described test vehicle and the soldering process, shall be used to conduct reproducible test data with respect to solderability, shelf life, and solder joint fatigue of components palladium lead finish. 6.1 Definition of the Test Vehicle The test vehicle consists of a printed wiring board with IC packages assembled using a reflow soldering process with defined parameters. 6.1.1 The Printed Wiring Board Specification of the printed wiring board. Substrate Type: FR4 with 4 layers of copper interconnection conformant with industry standard printed wiring boards. Dimensions: 203.2x152,4 mm (8" x 6"). Interconnection Layout: The layout shall fit the foot print pattern of the IC packages defined in 6.1.2. Thermal properties: The xy coefficient of thermal expansion (CTE) shall be in the range of 10 to 20 ppm/k. Tg 125 C. 6.1.2 The IC Packages Specification of the IC packages. Package size: The body size shall be according to IC product under test (PUT). IC Package configuration: Package under test shall have a lead frame metalized with the plating supplied by the IC component supplier. No internal daisy chain is required. Only mechanical samples are required. Material of package according to PUT. 3
Number of I/O: s: The Package number of I/O: s shall be according to PUT. The number of pins per IC component available for pull force measurement depends on the lead pitch. 6.2 The Soldering Process Specification of the soldering process. General: Reflow conditions and soldering materials specified cover conditions critical to soldering IC components with palladium. lead finish I/O temperature: Peak temperature at I/O lead shall not exceed 215 C and not be lower than 210 C Peak temperature: Time above I83 C should be between 30 s and 60 s, preferably not much more than 30 s. Solder paste: No-clean solder paste, non water soluble type RMA with no silver compounds. Reflow atmosphere: The atmosphere shall be air rather than nitrogen. Nitrogen makes the solder joints look better but has no impact on their reliability. Temperature Profile: The peak area of the reflow temperature profile should be within the shaded area in fig. 1. With respect to palladium specific solderability issues, the reflow profile in use should be equal to the lower curve (i.e. lower curve +5 C at max, time above 183 C not much longer than 30 s). 7 Properties The following tests are of interest: Properties of the palladium finish Properties of the solder joints 7.1 Properties of the Palladium Finish The following properties are of interest: The ductility of the palladium finish The porosity of the palladium finish Thickness of the palladium finish Solderability of the palladium finish Shelf life of the palladium finish 4
7.1.1 The Ductility of the Palladium Finish Test conditions: To be resolved. Need help with straw man Test Plan: The test shall be done once by the component supplier for every palladium finish construction released Supplier process control to keep ductility within the specified limit Criteria for acceptance: Minimum elongation of 15% must be met 7.1.2 The Porosity of the Palladium Finish Test conditions: To be resolved. Need help with straw man Test Plan: The test shall be done once by the component supplier for every palladium finish construction released Supplier process control to keep ductility within the specified limit Criteria for acceptance: To be resolved. Need help with straw man 7.1.3 Thickness of the Palladium Finish Test conditions: Test method for thickness measurements shall be described Test Plan: 1. Characterization of the palladium thickness shall be done once by the component supplier for every palladium finish construction released 2. Supplier process control to keep the thickness within specified limits Criteria for acceptance: Thickness of Nickel and Palladium shall be measured at the top and the bottom of the component lead (not on the rails). Measured thickness, using X-ray fluorescence, shall be: Minimum Maximum Palladium: 0.000003 inch (0.076 micro-meter) 0.000010 inch (0.254 micro-meter) Nickel: 0.000040 inch (1.00 micro-meter) 0.000120 inch (3.00 micro-meter) Since the X-ray fluorescence method can only report total palladium and total nickel, this approach can be practically used on various plating-layer systems. 7.1.4 Solderability of the Palladium Finish 7.1.4.1 Lead frames Test conditions: ANSI-J/Std 002 without steam age. Dry heat will be used instead of steam age as a preconditioning agent. Parameters of the solderability test: Hot Plate Temperature: 300ºC Time: 27-30 seconds Flux: R type Time at the flux: 10 seconds Time at the pot: 5 seconds Test Plan: The test shall be done once by the component supplier for every palladium finish 5
construction released Supplier process control to keep solderability above specified limit Criteria for acceptance: ANSI-J/Std 002 7.1.4.2 Components Test conditions: Ceramic Test Plate ANSI 638 Test Plan: The test shall be done once by the component supplier for every palladium finish construction released Supplier process control to keep solderability above specified limit Criteria for acceptance: ANSI 638 7.1.5 Shelf Life of Palladium Finish Test conditions: A set of components shall be tested according to the following stress schedule, where n=30 components are removed from each stress cell at shown intervals. Battelle Class 2 Corrosive environment shall be used. Test Plan: The test shall be done once by the supplier for every palladium lead finishing construction delivered. Criteria for acceptance: Analysis Sequence: (see Table 1) Comparison of the degradation rate under expected worst case assembly conditions in presence/absence of airborne pollutants with/without the attenuation effect of shipping container. Battelle Class 2 environment shall be used. Preconditioning 24 hours in this climate is equivalent to 2 years shelf life in industrial environment. Variable data shall be collected by means of pull testing leads of package under test. After each stress exposure, the subjected packages are stored away in a dry nitrogen cabinet, until all remaining samples have completed exposure. All packages should be soldered at the same time to minimize process and time-dependent (random order) effects. Table 1: Test procedure to determine the influence of aggressive gas 7.2 Properties of Solder Joints to Palladium Finish The reliability of the solder joint is of major concern. The reliability is characterized by: Visual inspection Destructive testing Testing of solder joint fatigue 7.2.1 Visual Appearance The visual appearance of the solder joints to palladium finished component leads differs from the appearance of leads having tin/lead finish. The results of the visual inspection are only partly in coincidence with the quality of the solder joints. Test conditions: Visual inspection shall be done according to ANSI/J-STD-001A level 2 Test Plan: The test shall be done once by the component supplier for every palladium finish construction released. Criteria for acceptance: ANSI / J-STD- 001A level 2 6
7.2.2 Destructive testing The destructive testing is done by: Measurement of pull forces at fracture Analysis of fracture areas Measurement of Pull Forces at Fracture Test conditions: Standard test method for pull force testing shall be used. A minimum number of 30 component leads shall be pulled off. Test Plan: The test shall be done once by the component supplier for every palladium finish construction released. Criteria for acceptance: The pull forces at fracture shall be??? 7.2.2.2 Analysis of Fracture Area Test conditions: See pull forces at fracture for generating fractures. Microscope with x?? magnification. Test Plan: The test shall be done once by the component supplier for every palladium finish construction released. Criteria for acceptance: The fracture region (between lead and pad) shall be porous. The fracture shall take place in the solder rather than in the interface area between the lead and solder 7.2.3 Fatigue of Solder Joints with Palladium Finish The crack growth of soldered connections shall be measured for test vehicles equipped with components which have: Tin/lead component lead finish. The purpose is to generate a reference set of data. Palladium component lead finish. Palladium thickness and deposit range shall be according to specification. The purpose is to generate to a fatigue set of data for palladium lead finish. Test conditions: Battelle Class 2 Corrosive environment shall be used. Prepare components for two groups of test vehicles, each consisting of 30 boards, shall be produced Expose the components of two groups to the equivalent 6 month shelf life acceleration; e. g. 24 hours exposure of Battelle Class 2 atmosphere. Reflow the test vehicles of both groups in the same process at the same time (randomized) using identical solder paste and reflow profile etc. Subject all test vehicles to temperature cycling stress according to schedule in Table 2 below, collection readout samples at the designated readout periods and statistically comparing degradation rates. Table 2: Test procedure to determine the influence of thermal cycling. 7
Test Plan: The test shall be done once by the component supplier for every palladium finish construction released. Criteria for acceptance: Results of all tests and the exact description of the tests performed shall be made available to the users. This would give them a chance to judge the conformance of the results with their requirements. 8 Definitions Component Lead: The connection of the component to the next level of packaging. Other names are: Lead, pin, terminal, I/O PWB: Printed Wiring Board the component is attached to. Other names are: Printed Circuit Board, substrate Supplier: Any supplier supplying components to a company assembling them to PWBs User: Any company assembling components to PWBs 8
Appendix 1 User Commitment Form Company: Business Unit: We accept the properties listed underneath if they are within the limits defined in document xxxxxxx Component Palladium Lead Finish - Specification. It is understood that the properties are established and maintained by: a. Results of the test performed by the supplier when releasing the palladium construction to the market. b. Process control applied to running production Properties: 7,1.1 Ductility 7.1.2 Porosity 7.1.3 Thickness 7.1.4 Solderability 7.1.5 Shelf Life 7.2.1 Visual Appearance 7.2.2.1 Pull Forces at Fracture 7.2.2.2 Fracture Area 7.2.3 Fatigue of Solder Joins 9
Appendix 2 Supplier Compliance Form Company: Business Unit: Name of Palladium Finish: Description of construction: Properties: Release Data Process Control 7.1.1 Ductility 7.1.2 Porosity 7.1.3 Thickness 7.1.4 Solderability 7.1.5 Shelf Life: 7.2.1 Visual Appearance 7.2.2.1 Pull Forces at Fracture 7.2.2.2 Fracture Area 7.2.3 Fatigue of Solder Joins Released Data Results of the test performed by the supplier when releasing the palladium construction to the market. All data are generated in the framework of document xxxxxxx Component Palladium Lead Finish - Specification, Process Control Description of the process control principles applied to running production. 10