Webinar High Performance PCB System Miniaturisation – HDI – Thermal Management – Printed Polymer www.we-online.de Webinar page 1 06.10.2015 Highly reliable printed circuit boards and devices in automotive electronics based on an example of a High Performance PCB System 1. Miniaturisation HDI Technology Reliability – IST 2. EmbR – printed embedded resistors Performance - Tolerances Reliability 3. Thermal Management Thermal vias Heat Sink Thermal Simulation Stefan Keller Product Manager 4. Costs www.we-online.de Webinar FR4 instead of Ceramic page 2 06.10.2015 High Performance PCB System Market Requirements Produkte Customer‘s objectives: PCB size and respectively the size of the unit needs to be reduced to one 1/4 in comparison to the currently running previous version Usage of complex and „small“ components High operating temperature (- 40 bis +140° C ambient temperature) Unchanged high long-term reliability, at least 10 years, 20.000 h (commercial vehicle application) Harsh environmental requirements e.g. vibration, mechanical shocks Cost effective - competitive Requirements for PCB manufacturer: Competent team: technology, process development, quality management Project management Test equipment Investment confidence www.we-online.de Webinar page 3 06.10.2015 High Performance PCB System Miniaturisation Produkte New PCB size: 1/4 1. Approach (temporary): LTCC – ceramic solution > works, but target only partially achieved – relatively expensive 2. Approach: High Performance organic (FR4) - PCB System 50 x 140 mm Combination of HDI- and Printed Polymer Technology in connection with optimized thermal management > Target achieved, production start at the beginning of 2015 www.we-online.de Webinar page 4 06.10.2015 High Performance PCB System Miniaturisation using HDI Technology Produkte PCB size / unit size > Could be essential for the success of a product! Long-standing recommendation of WE HDI Product Management: Reduction of the rooting area by using microvias + buried vias instead of plated through hole vias > perfectly implemented in the applicaton shown ! Buried Via Microvia Avoiding PTH Vias www.we-online.de Webinar page 5 06.10.2015 High Performance PCB System Miniaturisation by HDI Technologie Layer stack-up HDI06_2+2b+2 High packaging density by using Microvias + buried vias, without plated through (PTH) Vias 2nd Microvia layer Highest reliability caused by low PCB thickness < 1.0 mm (= low Z-axis expansion) Base material Low CTE TG 170°, filled, halogen free PTH vias are normally the weak points of a PCB concerning thermal cycle stability. www.we-online.de Webinar page 6 06.10.2015 High Performance PCB System Reliability - PCB Produkte Results of investigations: Thermal cycle tests -40° / +155° C (PCB + test coupons) IST Results: each 1000 cycles passed without any problems Further tests were carried out on the complete system. Investigations by customer on the unit as well. www.we-online.de Webinar page 7 06.10.2015 High Performance PCB System Reliability - PCB Interconnect Stress Test - IST The IST offers some decisive advantages to the conventional thermal cycle tests: 1000 Temperature - cycles in 4 days Online measurement of the measuring circuit IST = very meaningful test Special test coupon matched to the PCB design www.we-online.de Webinar page 8 06.10.2015 High Performance PCB System Reliability - IST Preparation: 6 x Reflow 245° C or 2 x 260° C Reflow-Simulation in IST or in accordance to customer specification Electrical heating of coupons through powercircuit to 150°C within 3 minutes, cooling to room temperature within 2 minutes Online measurement of temperature and resistance (+ 10 % max. resistance change permitted) www.we-online.de Webinar page 9 06.10.2015 High Performance PCB System Reliability - IST Measurement results HDI build-up (without PTH vias) TEST RESULTS Coupon ID 5209_10 5209_11 5209_14 5209_2 5209_5 5209_8 5209_9 Pwr Cycles 1000 1000 1000 1000 1000 1000 1000 Pwr % 0 -0.3 0.6 -0.1 -0.2 -0.5 -0.3 SenseA Cycles 1000 1000 1000 1000 1000 1000 1000 SnsA % 0.1 -0.2 0.6 -0.1 -0.2 -0.5 -0.2 SenseB Cycles 1000 1000 1000 1000 1000 1000 1000 SnsB % Results 0.2 -0.1 0.5 0.1 -0.3 -0.4 -0.3 Accept Accept Accept Accept Accept Accept Accept CusSpec N/A Mean Std Dev Min Max Range Coef Var Reliable produced Microvias have a high thermal cycle stability of significantly more than 1000 IST cycles (≙ 3000 conventional thermal cycles) N/A N/A TEST PROTOCOL: 334 ------------------------------------PASS------------------------------------ www.we-online.de Webinar page 10 06.10.2015 High Performance PCB System Reliability – Solder Process IPC-7095C: „max. 22% of the image diameter“ The appearance of voids depends on: Flux, solder paste Temperature profil ….. www.we-online.de Webinar page 12 06.10.2015 High Performance PCB System Reliability – Solder Process / Microvia Filling As both variants, filled and unfilled Microvias, have advantages and disadvantiges, WE does not give an recommendation. Everyone has to make their own decision! Copper Filling Filling = extra charge!! Filled & capped www.we-online.de Webinar page 13 06.10.2015 High Performance PCB System Printed Resistors – Printed Polymer in general Applications: • Pull-up and Pull-down resistors • Voltage dividers • General circuit resistors • High reliability requirements Facts: • Pastes with different resistance values • Tolerance printing process R +/- 30 % (standard) • Tolerance after laser trimming +/- 5 % for the entire product lifetime • Resistor values from 50Ω to 1 MΩ (standard) • Low temperature coefficient (≙ resistance change) +/- 300 ppm/K • Standard size min. 1,75 mm × 1,25 mm • Thickness of printed resistors approx. 20 µm • Design Rules available www.we-online.de Webinar page 14 06.10.2015 High Performance PCB System Printed Resistors – Printed Polymer WE: 10 years experience with printed resistors and with polymer pastes (carbon) - Miniaturisation using embedded resistors EmbR - Reliability advantages p Lenth R = ------- x -------0,02 Width p = paste resistance value www.we-online.de Webinar page 15 06.10.2015 High Performance PCB Systems Printed Resistors – Laser Trimming Tolerance of resistance value without laser trimming max. +/- 30% With Laser Trimming Process tolerance: down to +/- 1% Entire product lifetime: +/- 5% Traceability: The laser trimming process can also enable perfect traceability by using binary coding on additionally designed resistors. www.we-online.de Webinar page 16 06.10.2015 High Performance PCB System Printed Resistors – Choice of Pastes 1. Step: extensive investigations were necessary, in order to dertermine which pasts could fulfil the demanding requirements of the complete system. The stability of the resistance values under temperature influence was a particular challenge for many paste systems. Resistance change: 4 pastes @ 155° C operated with max. power www.we-online.de Webinar page 17 06.10.2015 High Performance PCB System Printed Resistors – Tests • Power Derating Aim of Power–Derating tests is to 2 Paste Rated Power at 70°C (mW/mm ) determine the max. electrical load of the WE-2D-250.1 179 resistor, but not to irreversibly damage WE-2D-10k.1 100 the resistor. Currant is constant. Result: even at 140° C the power dissipation is far above the disired 50 mW/mm². The performance of the printed resistors is at least as good as comparable soldered resistors or other embedded technologies. • Thermal Cycle Test (conventional) -40° C / + 155° C, 1000 cycles, transfer time max. 20 s, dwell time 15 Min., resistance change max. 2 % www.we-online.de Webinar page 18 06.10.2015 High Performance PCB System Printed Resistors – Tests Qualification of the System Resistors and Voltage Dividers Test Test method Procedure Max. Deviation Single Resistor Temperature Coefficient of Resistance (TCR) DIN EN 60115-1:2012-04, 4.8 +20 / -40°C ...+20°C / +140°C - 700 …– 300 ppm/K High Temperature Exposure (HTE) MIL-STD-202 Method 108 1000 h @ TA = 150° C unpowered +/- 3% Moisture Resistance MIL-STD-202 Method 106 25°/65°, 95% rH, 3 cycles in 24h, 10 days, unpowered +/- 2% Biased Humidity MIL-STD-202 Method 103 1000 h, 85°C, 85% rH, 10 % of operating power (50 mW/mm²) +/- 3% High Temperatur Operating Life (HTOL) MIL-STD-202 Method 108 1000h HTE, then 1000 h HTOL @ TA = 140° C at rated power +/- 20% Resistance to Soldering Heat IPC-TM650 5 times 260 +/- 5 ° C, 10 +/- 1 s +/- 2 % extract of the qualification programm The same tests have been done by customer on the assembled units. www.we-online.de Webinar page 19 06.10.2015 High Performance PCB System Printed Resistors – Tests Qualification of the System: Preparation HTOL www.we-online.de Webinar page 20 06.10.2015 High Performance PCB System Printed Resistors – Tests Annual Re-Qualificatin of the System Resistors and Voltage Dividers www.we-online.de Webinar page 21 06.10.2015 High Performance PCB System Thermal Management – in general Thermal Simulation Options on PCB basis: • Heat dissipation using vias • Heat spreading using planes and heatsinks glued onto the PCBs Target: • Lowering of temperature at the component • Avoiding critical temperatures inside of the component and unit • Extention of lifetime and ensure of long term reliability of the unit At threshold a thermal simulation in preliminary stages is recommended www.we-online.de Webinar page 22 Variant 2 Variant 3 06.10.2015 High Performance PCB System Thermal Management – PCB System Optimized Thermal Management • High number of Microvias (direcly in solder pads) and buried vias • Large cross section • Low thermal resistance Requirements on the system: Operating temperature 140° C, for short time 150°C ALU cooling element with high surface finish quality Thick wire bondable Sufficient adhesive strength in connection with thermal conductive adhesive • Thin thermal conductive adhesive 50 µm • EmbR very close to heat sink (cooling element) Solder resist Thermal conductive adhesive Cooling element New logistical challenge for the PCB manufacturer www.we-online.de Webinar page 23 06.10.2015 High Performance PCB System Thermal Management – Adhesive strength Verification of ahesive strength of PCB on cooling element Target: approx. 0.60 N/mm² Pretreatment Thermal cycles (-40°C / +155°C) 1000 cycles Climate chamber 1000 h (85°C / 85% air humidity) Hich temperature exposure (HTE Test) 1000 h in oven / 155°C Result: Necessary to ensure required adhesion strength: Lamination considering defined pressure, temperature and time parameters Surface tension ALU min. 38 mN/m www.we-online.de Webinar page 24 06.10.2015 High Performance PCB System Thermal Management – Simulation PCB bottom side Ambient temperature: 140°C Max. temperature at resistor: 153.5 °C Power in accordance with customer specifikation Thermal Simulation - Würth Elektronik CBT Product Management www.we-online.de Webinar page 25 06.10.2015 High Performance PCB System Thermal Management – Thermography Measurement PCB bottom side The thermography measurements essentially confirm the results of the simulation. As these measurements are very complex, only a limited number of resistors could be investigated. Ambient temperature 140° C Resistors powered with 5-30 V (HTOL Test) Measurement after 60 minutes www.we-online.de Webinar page 26 06.10.2015 High Performance PCB System Thermal Management – Thermography Measurement PCB Top side The thermography measurements show that critical hot spots, caused by powered resistors, are avoided, also on the PCB Top side. Ambient temperature 140° C Resistors powered with 5-30 V (HTOL Test) Measurement after 60 minutes www.we-online.de Webinar page 27 06.10.2015 High Performance PCB System Costs FR4 Ceramic • • High temperature resistance • • www.we-online.de Webinar page 28 High funktionality Highest packaging density Cost-efficient 06.10.2015 High Performance PCB System Costs – PCB in general Main advantage FR4 PCB: manufactured in „large“ production panels PCB Cost drivers Presented System PCB size + Unfavourable delivery panel / X-Out ++ Single PCB Complex build-up ≈ Material costs ++ Only one core, four pre-pregs, TG170 Mech. drilled vias ++ Only buried vias in a thin core Number of plating steps ≈ Only three „simple“ plating processes Complex contour machining + Simple milling contour www.we-online.de Webinar Relatively small size Two lamination processes page 29 06.10.2015 High Performance PCB System Requirements on PCB Manufacturer • • • • • • • • • • • • • • Metallurgic analysis Inspection according to IPC-6012 Class 3 Stereo/optical microscopy (VIS/UV) IR camera Ionograph CAF Measurement equipment Climate test chamber Thermal Cycle Test IST High Current Impulse Test Pressure Cooker Test X-Ray fluorescense spectroscopy Thermal simulation Testequipment for • HTOL • Power Derating Labview - controlled www.we-online.de Webinar page 30 Collaboration with institus • • • • • REM/EDX (Uni Basel, EMPA Zürich) FIB (Uni Basel, EMPA Zürich) XPS (IGB Stuttgart) Wetting tests (ISIT Itzehoe) Ultrasonic microscopy (ISIT Itzehoe) 06.10.2015 High Performance PCB System Summary • Miniaturisation by - HDI Technology - Printed resistors (Printed Polymer) • Highest reliability using a thin HDI build-up without PTH vias • A technology combination of - HDI - Printed resistors - Optimized Thermal Management can enable a cost effective substitution of a ceramis solution by a FR4 - PCB • A competent and broadly based PCB manufacturer can realize such a task. System solutions will be an essential part of collaboration in the future. www.we-online.de Webinar page 31 06.10.2015 Produkte Systeme Dienstleistungen Knowing the relationships - is a secret of success! We are looking forward to good cooperation! Stefan Keller Product Manager [email protected] www.we-online.de Webinar page 32 06.10.2015