? semiconductor components industries, llc, 2000 october, 2000 ? rev. 3 371 publication order number: mr2500/d mr2502, mr2504, MR2510 mr2504 and MR2510 are preferred devices medium-current silicon rectifiers . . . compact, highly efficient silicon rectifiers for medium?current applications requiring: ? high current surge e 400 amperes @ t j = 175 c ? peak performance @ elevated temperature e 25 amperes @ t c = 150 c ? low cost ? compact, molded package e for optimum efficiency in a small case configuration mechanical characteristics: ? case: epoxy, molded ? weight: 1.8 grams (approximately) ? finish: all external surfaces corrosion resistant and terminals are readily solderable ? lead temperature for soldering purposes: requires a custom temperature soldering profile ? polarity: cathode polarity band ? shipped 5000 units per box maximum ratings please see the table on the following page device package shipping ordering information microde button case 193 http://onsemi.com mr2502 microde button 5000 units/box mr2504 microde button 5000 units/box MR2510 microde button 5000 units/box medium?current silicon rectifiers 25 amperes 200?1000 volts diffused junction preferred devices are recommended choices for future use and best overall value. marking diagram mr25xx = device code xx = 02, 04 or 10 l = location code yy = year ww = work week mr25xx lyyww
mr2502, mr2504, MR2510 http://onsemi.com 372 maximum ratings characteristic symbol mr2502 mr2504 MR2510 unit peak repetitive reverse voltage working peak reverse voltage dc blocking voltage v rrm v rwm v r 200 400 1000 volts non?repetitive peak reverse voltage (halfwave, single phase, 60 hz peak) v rsm 240 480 1200 volts average rectified forward current (single phase, resistive load, 60 hz, t c = 150 c) i o 25 amps non?repetitive peak surge current (surge applied at rated load conditions, halfwave, single phase, 60 hz) i fsm 400 (for 1 cycle) amps operating and storage junction temperature range t j , t stg 65 to +175 c thermal characteristics characteristic symbol max unit thermal resistance, junction to case (single side cooled) r q jc 1.0 c/w electrical characteristics characteristics and conditions symbol max unit maximum instantaneous forward voltage (i f = 78.5 amps, t c = 25 c) v f 1.18 volts maximum reverse current (rated dc voltage) t c = 25 c t c = 100 c i r 100 500 m a
mr2502, mr2504, MR2510 http://onsemi.com 373 figure 1. forward voltage figure 2. non?repetitive surge current figure 3. forward voltage temperature coefficient figure 4. current derating figure 5. forward power dissipation 1.8 2.4 0.6 v f , instantaneous forward voltage (volts) 700 500 20 50 10 number of cycles 100 1.0 300 100 80 60 i f , instantaneous forward current (amp) 1.0 0.2 +0.5 0 -0.5 -1.0 -1.5 -2.0 2.0 130 140 125 t c , case temperature ( c) 40 30 20 10 0 i f(av) , average forward current (amp) 10 0 50 40 30 10 0 40 135 i f , instantaneous forward current (amp) i coefficient (mv/ c) 5.0 2.0 1.0 1.2 0.8 1.0 1.4 1.6 2.0 2.2 2.0 5.0 10 20 50 200 400 600 10 20 100 200 , average forward current (amp) i f(av) 145 155 150 50 20 30 50 20 p f(av) , average power dissipation (watts) 2.6 7.0 100 70 0.2 0.5 0.7 200 30 3.0 0.3 300 , peak half wave current (amp) fsm 0.5 5.0 50 160 165 175 170 maximum typical t j = 25 c typical range f = 60 hz t j = 175 c 25 c sine wave capacitive loads i (fm) i (av) 20 capacitive loads 5.0 10 20 dc i (fm) i (av) (sinewaveresistiveload) sine wave resistive load square wave dc 5.0 10 1 cycle v rrm may be applied between each cycle of surge. the t j noted is t j prior to surge
mr2502, mr2504, MR2510 http://onsemi.com 374 to determine maximum junction temperature of the diode in a given situation, the following procedure is recommended: duty cycle, d = t p /t 1 peak power, p pk , is peak of an equivalent square power pulse. the temperature of the case should be measured using a thermocouple placed on the case at the temperature reference point (see the outline drawing on page 1). the thermal mass connected to the case is normally large enough so that it will not significantly respond to heat surges generated in the diode as a result of pulsed operation once steady?state conditions are achieved. using the measured value of t c , the junction temperature may be determined by: t j = t c + t jc where t jc is the increase in junction temperature above the case temperature, it may be determined by: t jc = p pk r q jc [d + (1 d) r(t 1 + t p ) + r(t p ) r(t 1 )] where r(t) = normalized value of transient thermal resistance at time, t, from figure 6, i.e.: r (t 1 + t p ) = normalized value of transient thermal resistance at time t 1 + t p. t 1 t p p pk p pk time figure 6. thermal response figure 7. capacitance figure 8. forward recovery time figure 9. reverse recovery time t, time (ms) 100 1.0 0.5 0.07 0.05 0.01 v r , reverse voltage (volts) 1.0 0.1 500 300 200 100 70 50 2.0 1.0 i f , forward current (amp) 0.7 0.5 0.3 0.2 0.1 i r /i f , ratio of reverse to forward current 0.2 0.1 20 7.0 5.0 2.0 1.0 7.0 2.0 c, capacitance (pf) 2.0 5.0 10 20 50 0.3 0.7 1.0 10 20 100 , forward recovery time ( s) t fr 5.0 3.0 1.0 0.3 0.5 10 3.0 t rr , reverse recovery time ( s) 0.2 5.0 50 7.0 10 r(t), transient thermal resistance 0.2 0.1 0.03 0.02 0.05 0.07 0.1 0.2 0.3 0.5 0.7 3.0 30 200 300 500 0.5 10 0.7 1.0 2.0 3.0 5.0 7.0 70 r jc(t) = r jc ? r(t) note 1 t j = 25 c all devices all devices except mr2500 2.0 v fr = 1.0 v t j = 25 c t j = 25 c i f = 10 a 5.0 a 1.0 a fr f t fr i f 0 i r 0.25 i r t rr (normalized)
mr2502, mr2504, MR2510 http://onsemi.com 375 figure 10. rectification waveform efficiency f, frequency (khz) 2.0 1.0 60 20 10 6.0 70 3.0 5.0 100 8.0 , efficiency factor 40 7.0 10 20 30 50 t j = 25 c current input waveform figure 11. single?phase half?wave rectifier circuit rectification efficiency note r s r l v o the rectification efficiency factor s shown in figure 10 was calculated using the formula: s p (dc) p (rms) v 2 o (dc) r l v 2 o (rms) r l . 100% v 2 o (dc) v 2 o ( ac) v 2 o (dc) . 100% (1) for a sine wave input v m sin ( w t) to the diode, assume lossless, the maximum theoretical efficiency factor becomes: s (sine) v 2 m 2 r l v 2 m 4r l . 100% 4 p 2 . 100% 40.6% (2) for a square wave input of amplitude v m , the efficiency factor becomes: s (square) v 2 m 2 r l v 2 m r l . 100% 50% (3) (a full wave circuit has twice these efficiencies) as the frequency of the input signal is increased, the reverse recovery time of the diode (figure 9) becomes significant, resulting in an increasing ac voltage component across r l which is opposite in polarity to the forward current, thereby reducing the value of the efficiency factor s , as shown on figure 10. it should be emphasized that figure 10 shows waveform efficiency only; it does not provide a measure of diode losses. data was obtained by measuring the ac component of v o with a true rms ac voltmeter and the dc component with a dc voltmeter. the data was used in equation 1 to obtain points for figure 10.
mr2502, mr2504, MR2510 http://onsemi.com 376 assembly and soldering information there are two basic areas of consideration for successful implementation of button rectifiers: 1. mounting and handling 2. soldering each should be carefully examined before attempting a finished assembly or mounting operation. mounting and handling the button rectifier lends itself to a multitude of assembly arrangements but one key consideration must always be included: one side of the connections to the button must be flexible! this stress relief to the button should also be chosen for maximum contact area to afford the best heat transfer e but not at the expense of flexibility. for an annealed copper terminal a thickness of 0.015 is suggested. the base heat sink may be of various materials whose shape and size are a function of the individual application and the heat transfer requirements. common materials advantages and disadvantages steel low cost; relatively low heat conductivity copper high cost; high heat conductivity aluminum medium cost; medium heat conductivity relatively expensive to plate and not all platers can process aluminum. handling of the button during assembly must be relatively gentle to minimize sharp impact shocks and avoid nicking of the plastic. improperly designed automatic handling equipment is the worst source of unnecessary shocks. techniques for vacuum handling and spring loading should be investigated. the mechanical stress limits for the button diode are as follows: compression 32 lbs. 142.3 newton tension 32 lbs. 142.3 newton torsion 6?inch lbs. 0.68 newton?meters shear 55 lbs. 244.7 newton tension compression torsion shear mechanical stress exceeding these recommended maximums can result in electrical degradation of the device. soldering the button rectifier is basically a semiconductor chip bonded between two nickel?plated copper heat sinks with an encapsulating material of thermal?setting silicone. the exposed metal areas are also tin plated to enhance solderability. in the soldering process it is important that the temperature not exceed 250 c if device damage is to be avoided. v arious solder alloys can be used for this operation but two types are recommended for best results: 1. 95% sn, 5% sb; melting point 237 c 2. 96.5% tin, 3.5% silver; melting point 221 c 3. 63% tin, 37% lead; melting point 183 c solder is available as preforms or paste. the paste contains both the metal and flux and can be dispensed rapidly. the solder preform requires the application of a flux to assure good wetting of the solder. the type of flux used depends upon the degree of cleaning to be accomplished and is a function of the metals involved. these fluxes range from a mild rosin to a strong acid; e.g., nickel plating oxides are best removed by an acid base flux while an activated rosin flux may be sufficient for tin plated parts. since the button is relatively light?weight, there is a tendency for it to float when the solder becomes liquid. to prevent bad joints and misalignment it is suggested that a weighting or spring loaded fixture be employed. it is also important that severe thermal shock (either heating or cooling) be avoided as it may lead to damage of the die or encapsulant of the part. button holding fixtures for use during soldering may be of various materials. stainless steel has a longer use life while black anodized aluminum is less expensive and will limit heat reflection and enhance absorption. the assembly volume will influence the choice of materials. fixture dimension tolerances for locating the button must allow for expansion during soldering as well as allowing for button clearance. heating techniques the following four heating methods have their advantages and disadvantages depending on volume of buttons to be soldered. 1. belt furnaces readily handle large or small volumes and are adaptable to establishment of aon?line'' assembly since a variable belt speed sets the run rate. individual furnace zone controls make excellent temperature control possible. 2. flame soldering involves the directing of natural gas flame jets at the base of a heatsink as the heatsink is indexed to various l oading?heating?cooling?unloading positions. this is the most economical labor method of soldering large volumes. flame soldering offers good temperature control but requires sophisticated temperature monitoring systems such as infrared. strain relief terminal for button rectifier copper terminal button base (heat sink material)
mr2502, mr2504, MR2510 http://onsemi.com 377 assembly and soldering information (continued) 3. ovens are good for batch soldering and are production limited. there are handling problems because of slow cooling. response time is load dependent, being a function of the watt rating of the oven and the mass of parts. large ovens may not give an acceptable temperature gradient. capital cost is low compared to belt furnaces and flame soldering. 4. hot plates are good for soldering small quantities of prototype devices. temperature control is fair with overshoot common because of the exposed heating surface. solder flow and positioning can be corrected during soldering since the assembly is exposed. investment cost is very low. regardless of the heating method used, a soldering profile giving the time?temperature relationship of the particular method must be determined to assure proper soldering. profiling must be performed on a scheduled basis to minimize poor soldering. the time?temperature relationship will change depending on the heating method used. solder process evaluation characteristics to look for when setting up the soldering process: i overtemperature is indicated by any one or all three of the following observations. 1. remelting of the solder inside the button rectifier shows the temperature has exceeded 285 c and is noted by aislands'' of shiny solder and solder dewetting when a unit is broken apart. 2. cracked die inside the button may be observed by a moving reverse oscilloscope trace when pressure is applied to the unit. 3. cracked plastic may be caused by thermal shock as well as overtemperature so cooling rate should also be checked. ii cold soldering gives a grainy appearance and solder build?up without a smooth continuous solder fillet. the temperature must be adjusted until the proper solder fillet is obtained within the maximum temperature limits. iii incomplete solder fillets result from insufficient solder or parts not making proper contact. ivtilted buttons can cause a void in the solder between the heatsink and button rectifier which will result in poor heat transfer during operation. an eight degree tilt is a suggested maximum value. v plating problems require a knowledge of plating operations for complete understanding of observed deficiencies. 1. peeling or plating separation is generally seen when a button is broken away for solder inspection. if heatsink or terminal base metal is present the plating is poor and must be corrected. 2. thin plating allows the solder to penetrate through to the base metal and can give a poor connection. a suggested minimum plating thickness is 300 microinches. 3. contaminated soldering surfaces may out?gas and cause non?wetting resulting in voids in the solder connection. the exact cause is not always readily apparent and can be because of: (a) improper plating (b) mishandling of parts (c) improper and/or excessive storage time solder process monitoring continuous monitoring of the soldering process must be established to minimize potential problems. all parts used in the soldering operation should be sampled on a lot by lot basis by assembly of a controlled sample. evaluate the control sample by break?apart tests to view the solder connections, by physical strength tests and by dimensional characteristics for part mating. a shear test is a suggested way of testing the solder bond strength. post soldering operation considerations after soldering, the completed assembly must be unloaded, washed and inspected. unloading must be done carefully to avoid unnecessary stress. assembly fixtures should be cooled to room temperature so solder profiles are not affected. washing is mandatory if an acid flux is used because of its ionic and corrosive nature. wash the assemblies in agitated hot water and detergent for three to five minutes. after washing; rinse, blow off excessive water and bake 30 minutes at 150 c to remove trapped moisture. inspection should be both electrical and physical. any rejects can be reworked as required. summary the button rectifier is an excellent building block for specialized applications. the prime example of its use is the output bridge of the automative alternator where millions are used each year. although the material presented here is not all inclusive, primary considerations for use are presented. for further information, contact the nearest on semiconductor sales office or franchised distributor.
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