Assembly Instructions

Transcription

1 Assemby Instructions GENERAL Optoeectronic semiconductor devices can be mounted in any position. Connection wires may be bent provided the bend is not ess than 1.5 mm from the bottom of the case. During bending, no forces must be transmitted from the pins to the case (e.g., by spreading the pins). If the device is to be mounted near heat generating components, the resutant increase in ambient temperature must be taken into account. INSTRUCTIONS Protection against overheating is essentia when a device is being sodered. It is recommended, therefore, that the connection wires are eft as ong as possibe. The time during which the specified maximum permissibe device junction temperature is exceeded at the sodering process shoud be as short as possibe (one minute maximum). In the case of pastic encapsuated devices, the maximum permissibe sodering temperature is governed by the maximum permissibe heat that may be appied to the encapsuant rather than by the maximum permissibe junction temperature. The maximum sodering iron (or soder bath) temperatures are given in Tab. 1. At temperatures far above the gass transition point, the epoxy softens pasticay. During sodering, no forces must be transmitted from the pins to the case (e.g., by spreading the pins or by creation of mechanica tension during devices insertion, cinching or crimping processes). Devices in pastic case 3 mm Devices in pastic case < 3 mm IRON TEMPERATURE 26 C 3 C IRON DISTANCE OF THE POSITION FROM THE LOWER EDGE OF THE CASE 2. mm 5. mm MAXIMUM ALLOWABLE SEE TEMPERATURE- TIME 3 s TEMPERATURE FROM THE LOWER TIME PROFILES 235 C 26 C WAVE DISTANCE OF THE POSITION EDGE OF THE CASE 2. mm 2. mm MAXIMUM ALLOWABLE TIME 3 C 5. mm 3 s 26 C 2. mm 3 s TELUX 26 C 2. mm 26 C 1.5 mm SMD n.a n.a n.a 26 C n.a Mini n.a n.a n.a n.a n.a n.a 63 LED n.a n.a n.a n.a n.a n.a Tabe 1. Maximum Sodering Temperatures MOISTURE SENSITIVITY LEVELS (JEDEC LEVEL) SOAK REQUIREMENTS FLOOR LIFE STANDARD ACCELERATED EQUIVALENT LEVEL TIME CONDITIONS TIME (HOURS) CONDITIONS TIME (HOURS) CONDITIONS 1 Unimited 3 C/85 % RH /- 85 C/85 % RH 2 1 year 3 C/85 % RH /- 85 C 6 % RH 2a 4 weeks 3 C/85 % RH /- 3 C/6 % RH /- 6 C/6 % RH hours 3 C/85 % RH /- 3 C/6 % RH /- 6 C/6 % RH 4 72 hours 3 C/85 % RH /- 3 C/6 % RH /- 6 C/6 % RH 5 48 hours 3 C/85 % RH /- 3 C/6 % RH /- 6 C/6 % RH 5a 24 hours 3 C/85 % RH /- 3 C/6 % RH /- 6 C/6 % RH 6 Time on Labe (TOL) 3 C/85 % RH TOL 3 C/6 % RH Tabe 2. JEDEC Leve 8 s 1

2 METHODS There are severa methods in use to soder devices on to the substrate. Some of them are isted in the foowing: (a) Sodering in the vapor phase Sodering in saturated vapor is aso known as condensation sodering. This sodering process is used as a batch system (dua vapor system) or as a continuous singe vapor system. Both systems may aso incude preheating of the assembies to prevent high temperature shock and other undesired effects. (b) Refow sodering The heating rate in an IR furnace depends on the absorption coefficients of the materia surfaces and on the ratio of the component s mass to its irradiated surface. The temperature of parts in an IR furnace, with a mixture of radiation and convection, cannot be determined in advance. Temperature measurement may be performed by measuring the temperature of a certain component whie it is beeing transported through the furnace. The temperatures of sma components, sodered together with arger ones, may rise up to 28 C. Infuencing parameters on the interna temperature of the component are as foows: Time and power Mass of the component Size of the component Size of the printed circuit board Absorption coefficient of the surfaces Packing density Waveength spectrum of the radiation source Ratio of radiated and convected energy Temperature-time profies of the entire process and the infuencing parameters are given in figure 1. (c) Wave sodering In wave sodering, one or more continuousy repenished waves of moten soder are generated, whie the substrates to be sodered are moved in one direction across the wave s crest. Temperature-time profies of the entire process are given in figure 2. (d) Iron sodering This process cannot be carried out in a controed way. It shoud not be considered for use in appications where reiabiity is important. There is no SMD cassification for this process. (e) Laser sodering This is an excess heating sodering method. The energy absorbed may heat the device to a much higher temperature than desired. There is no SMD cassification for this process at the moment. (f) Resistance sodering This is a sodering method which uses temperature controed toos (thermodes) for making soder joints. There is no SMD cassification for this process at the moment. (g) Soderabiity of parts with pure tin pating and SnPb soder at ower temperature. Sodering of parts can aso be processed beow 215 C. In a test the soderabiity of SMD LEDs in PLCC2 package was tested with: Pating Sn 1-18 µm on CuFe ead frame Pre aging 155 C, 4 h Bath temperature 25 C Dipping time 2 s A the sampes showed 1 % wetting after this test and the diffusion of the SnPb in the Sn surface was competed. To check the soderabiity of individua parts on ower sodering temperatures we recommend to do an suitabe test ike the above one. Warning Devices in PLCC-packages are sensitive to moisture reease if they are subjected to infrared refow or a simiar soder process (e.g. wave sodering). After opening the bag, they must be: 1. stored at ambient of < 2 % reative humidity (RH) 2. mounted within required time acc. Jedec Leve printed on abe. (< 3 C/6 % RH) Devices require baking before mounting if 1. or 2. is not met and humidity indicator card is > 2 % at 23 ± 5 C. If baking is required, devices may be baked for 192 hours at 4 C + 5 C - C and < 5 % RH. For any devices avoid any mechanica stress on the package via the eads. 2

3 TEMPERATURE-TIME PROFILES C 24 C 217 C IR Refow Sodering Profie for Lead (Pb)-free Sodering Preconditioning acc. to JEDEC Leve 2a max. 12 s max. ramp up 3 C/s max. 3 s max. 1 s max. 26 C 245 C max. ramp down 6 C/s max. 2 cyces aowed Figure 1. Vishay Lead (Pb)-free Refow Sodering Profie (acc. to J-STD-2C) max. 24 C ca. 23 C 1 s 2 K/s to 4 K/s C max. 16 C 9 s to 12 s 1 15 max 4 s Lead Temperature Fu Line: Typica Dotted: Process Limits Figure 2. Vishay Lead (Pb)-free Refow Sodering Profie 3 15 forced 1 1 C to 13 C cooing ca. 5 K/s C to 26 C first wave ca. K/s 2 K/s second wave ca. 2 K/s Lead Temperature fuine: typica dotted ine: process imits HEAT REMOVAL To keep the therma equiibrium, the heat generated in the semiconductor junction(s) during operation wi aways move to outside the device. In the case of ow power devices, the natura heat conductive path between the case and surrounding air is usuay adequate for this purpose. The heat generated in the junction is conveyed to the case or header by conduction rather than convection. A measure of the effectiveness of heat conduction is the inner therma resistance or therma resistance junction case, R thjc, the vaue of which is governed by the construction of the device. Any heat transfer from the case to the surrounding air invoves radiation convection and conduction, the effectiveness of transfer being expressed in terms of an R thca vaue, i.e., the externa or case ambient therma resistance. The tota therma resistance, junction ambient is consequenty: R thja = R thjc + R thca The tota maximum power dissipation, P totmax of a semiconductor device can be expressed as foows: T P jmax T amb T totmax jmax T = = amb R thja R thjc + R thca where: T jmax the maximum aowabe junction temperature T amb the highest ambient temperature ikey to be reached under the most unfavorabe conditions R thjc the therma resistance, junction case R thja the therma resistance, junction ambient, is specified for the components. The foowing diagram shows how the different instaation conditions effect the therma resistance R thca the therma resistance, case ambient, depends on cooing conditions. If a heat dissipator or sink is used, R thca depends on the therma contact between case and heat sink, heat propagation conditions in the sink and the rate at which heat is transferred to the surrounding air. For further detais about therma management see TELUX Appication Note Figure 3. Doube wave sodering of opto devices (a packages) 3

4 1 b R thja (%) 9 c a Length (mm) Figure 4. Therma resistance junction / ambient vs. ead ength.14 mm 2 Cu isoated Figure 6. In the case of wire contacts (curve b, figure 3) Cu 2.5 From underneath 2.5 From underneath mm 2 Cathode Side view Side view Figure 5. In the case of assemby on PC board with heatsink (curve a, figure 3) Figure 7. In the case of assemby on PC board, no heatsink (curve c, figure 3) 4

5 CLEANING Sodered assembies are washabe with the foowing sovents: 1. A mixture of 1, 1.2-trichorotrifuoroethane, 7 ± 5 % by weight and 2-propano (isopropy acoho), 3 ± 5 % by weight. Commerciay avaiabe grades (industria use) shoud be used.warning: The component 1, 1.2-trichorofuoroethane is hazardous to the environment. Therefore this sovent must not be used where the sovent specified in 2 or 3 is adquate propano (isopropy acoho). Commerciay avaiabe grades (industria use) shoud be used. 3. Demineraized or distied water having a resistivity of not ess than 5 mω corresponding to a conductivity of 2 ms/m Caution: The use of tetrachor, acetone, trichoroetyene or simiar is NOT ALLOWED! WARNING Exceeding any one of the ratings (sodering, ceaning or short time exceeding the raiings) coud resut in irreversibe changes in the ratings. 5