2025 Electronic Potting Material Selection Guide: Epoxy vs Polyurethane vs Silicone - Kev sib piv
Executive Summary
Xaiv txoj cai potting / encapsulation compound rau cov khoom siv hluav taws xob cuam tshuam rau kev ua haujlwm thermal, kev tiv thaiv kev siv tshuab, hluav taws xob rwb thaiv tsev, kev tswj kev ntxhov siab, kev tsim khoom, thiab tag nrho cov nqi ntawm cov tswv cuab.
Epoxy: High rigidity, zoo heev adhesion thiab tshuaj tiv thaiv, zoo hluav taws xob rwb thaiv tsev. Feem ntau muaj kev tiv thaiv zoo dua qub, tiam sis tuaj yeem ua rau thermal -txoj kev nyuaj siab ntawm cov khoom siv vim muaj kev hloov pauv siab. Tsim nyog qhov chaw muaj kev tiv thaiv kev tiv thaiv thiab siab dielectric zog yog qhov tseem ceeb.
Polyurethane (PU): Nruab nrab modulus thiab ntau dua toughness; tus nqi- zoo; zoo dua rau kev co thiab kev poob siab. PU formulations sib txawv nyob rau hauv cov dej rhiab heev rhiab heev - xaiv ib tug zoo stabilized PU yog ib qho tseem ceeb.
Silicone: Modulus qis tshaj plaws thiab kev ua tau zoo tshaj plaws nyob rau qhov kub thiab txias; tuav elasticity, txo kev ntxhov siab ntawm cov khoom; feem ntau cov nqi siab dua thiab qis adhesion tsis muaj primers. Qhov zoo tshaj plaws rau kev caij tsheb kauj vab thiab qhov kub thiab txias - ntau yam kev siv.
1. Chemical Basis thiab Kho Mechanisms
Epoxy
Ob -cov khoom siv thermosetting tshuab (resin + curing agent). Crosslinking tsim cov kev sib txuas ruaj khov; Cov khoom xws li modulus, Tg, thiab tshuaj tiv thaiv yog nyob ntawm resin chemistry thiab kho tus neeg sawv cev.
Polyurethane
Feem ntau A/B systems tsim urethane linkages. Shore hardness thiab yoog raws nyob ntawm kev xaiv polyol / isocyanate. Qee cov PUs rhiab heev rau cov dej noo thaum ua haujlwm-cov dej noo reacts nrog isocyanates tsim CO₂ thiab muaj peev xwm ua npuas dej.
Silicone
Siloxane caj qaum muab qhov tshwj xeeb thermal stability thiab qis -kub yooj yim. RTV silicones (ntxiv - los yog condensation- kho) muaj nyob rau hauv ib qho - lossis ob - cov tshuab.
2. Cov ntaub ntawv tseem ceeb tsis tau (yuav ua tib zoo nyeem dab tsi)
Thaum kuaj cov neeg sib tw, paub meej tias:
Lub neej lub lauj kaub / lub sijhawm ua haujlwm thiab kev kho tag nrho- cuam tshuam kev tsim khoom.
viscosity- tseem ceeb heev rau ntws thiab ntub dej; qhia hauv cP/mPa·s.
Tshwj xeeb lub ntiajteb txawj nqus- qhia tias qhov chaw muab tub lim rau thermally conductive versions.
Thermal service range, CTE, thermal conductivity- tseem ceeb heev rau cov cua kub dissipation & thermo-kev tswj kev ntxhov siab.
Mechanical zog: Shore hardness, tensile zog, elongation- txhais tau tias kev poob siab thiab kev vibration.
Cov khoom siv hluav taws xob: dielectric zog, dielectric tas li, ntim resistivity- qhov tseem ceeb rau high -voltage lossis RF daim ntawv thov.
Tshuaj thiab humidity kuj- xyuas HAST/85/85 kev ntaus nqi thiab tshuaj lom neeg sib raug zoo.
Tsis yog -corrosive rau tooj liab- yuav tsum tau hais meej meej thaum potting ze ntawm cov kab tooj liab raug.
3. Kev sib piv (mechanical, thermal, hluav taws xob, tshuaj, adhesion)
Mechanical & Stress Management
Epoxy: High modulus-kev txhawb zog zoo, tab sis nws yooj yim rau tawg qhov twg CTE tsis sib haum.
PU: Tsawg modulus thiab siab dua toughness -zoo dua poob siab.
Silicone: Modulus qis tshaj plaws thiab elongation siab tshaj plaws -zoo tshaj plaws rau kev caij tsheb kauj vab thiab kev ntxhov siab tsawg.
Kub
Siab -kub stability: Silicone > Epoxy (vary los ntawm formulation) > PU.
Thermal conductivity: Lub hauv paus polymers yog cov neeg ua haujlwm tsis zoo - cov khoom ntim khoom yuav tsum tau ua rau kev tswj xyuas thermal. Ob qho tib si epoxy thiab silicone tuaj yeem tsim rau hauv cov qib thermally conductive.
Hluav taws xob
Dielectric zog: Epoxy thiab silicone feem ntau muab cov rwb thaiv tsev zoo.
Tshuaj thiab Moisture Resistance
Epoxy: Feem ntau cov tshuaj tiv thaiv zoo tshaj plaws thiab kev nqus dej tsawg.
PU: Hloov pauv; qee cov PUs yuav soften los yog nqus cov dej noo- tshawb xyuas qhov ntev - lub sij hawm ntub dej kub ua haujlwm.
Silicone: Zoo weatherability & stability; additive migration yuav tsum tau txiav txim siab rau rhiab optics los yog sensors.
Adhesion
Epoxy > PU > Silicone (silicones feem ntau xav tau primers).
4. Kev xav txog kev tsim khoom
Degassing: Nqus degassing feem ntau yuav tsum tau (tshwj xeeb tshaj yog rau cov puv, siab -viscosity systems).
Mix ratio & raug: Qhov tseem ceeb rau 2K tshuab (ob leeg epoxy thiab PU). Qhov sib piv tsis raug=kho tsis tiav & txo cov khoom.
Kho exotherm: Saib xyuas thiab txwv ntu tuab kom tsis txhob muaj kev puas tsuaj thermal.
Txheej txheem lub sij hawm: Optimize lauj kaub lub neej vs kho lub sij hawm raws li ntau lawm xav tau; qee lub tshuab kho sai nrog qhov kub siab.
5. Kev ntsuam xyuas kev ntseeg tau & hom kev ua tsis tiav
Thermal cycling: Txheeb xyuas qhov tawg (epoxy) thiab delamination.
Damp kub / HAST: Ntsuas cov dej ingress cuam tshuam rau lub zog dielectric.
Kev vibration & shock: Ntsuam xyuas cov neeg kho tshuab loosening lossis tawg propagation. PU feem ntau ua tau zoo dua hauv cov xwm txheej poob siab.
6. Kev Xaiv Ua Haujlwm Ua Haujlwm (Conservative)
Txhais ib puag ncig, hluav taws xob, mechanical, thermal, thiab kev pabcuam lub neej.
Qib qhov tseem ceeb (piv txwv li, qhov kub thiab txias> adhesion> nqi).
Ua ntej-cov ntaub ntawv tshuaj ntsuam.
Lab sim: potting, degassing, kho, interface adhesion tests.
Kev ntsuas kev ntseeg tau: thermal voj voog, damp cua sov, kev co.
Scale- nce & kev tsim nyog (SOP, PFMEA).
Sau cov ntaub ntawv ua raws (CoA MSDS, UL cov ntaub ntawv).
7. Cov lus pom zoo ntawm daim ntawv thov (Conservative)
Aerospace/High Temp: Silicone (siab- qib kub).
Transformers / Relays / High Voltage: Epoxy rau rwb thaiv tsev & tshuaj tiv thaiv.
Consumer/General Industrial (kev vibration{0}}nruab nrab): PU (validated rau noo noo stability).
