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Precision Clamps and Heat Sink Assemblies Heat Sink SCR IGBT Assemblies Wakefield-Vette compression pack heat sink and clamp systems provide customers with the complete system solution for proper installation and heat dissipation for high-power compression pack semiconductors. These high-quality mounting clamp assemblies are the industry standard for mounting, compressing, and clamping press-pack SCR, thyristors, rectifiers, and other high power disc packaged devices. Devices of these styles are most commonly found in power distribution equipment, industrial controls, transportation systems, and power supply and conversion systems. A clamp system consists of a crossbar and a spring assembly. The crossbar is a steel bar with two threaded rods installed in it. The rods are generally knurled and cold rolled into the bar to ensure proper fit. The cross bar assembly is covered in an epoxy coating which acts as an electrical insulator to ensure the devices are properly grounded. The crossbar is installed through the center web of the heat sink and sits in a channel surrounded by fins needed for thermal performance. On the back of the heat sink, a puck style device is installed and then the spring assembly is installed in the threaded rods of the crossbar. By tightening the nuts on the spring assembly, a compression force is applied to the center of the puck. Each spring assembly has a force gauge integrated into it to ensure ease of assembly and consistency of force applied to the many devices used in a system. The cross bar assembly is available in various lengths to meet the various needs of the industry. All components for device mounting are available separately for all standard compression requirements from 800 lbs. to 16,000 lbs. www.wakefield-vette.com PRECISION CLAMP HEAT SINKS PRECISION CLAMP HEAT SINKS PRECISION COMPRESSION MOUNTING CLAMP SYSTEMS Wakefield-Vette Engineering compression pack heat sinks and clamp systems provide electrical and industrial equipment manufacturers with complete system solutions for proper installation and heat dissipation for high-power compression pack semiconductor. All components for device mounting and cooling are available separately for all standard compression requirements from 800 lbs (362.9 kg) to 16,000 lbs (7,257.5 kg) force in both natural and forced convection applications. Clamp Assembly Series 130 Series 139 Series 143 Series 144 Series 145 Series 146 Series 131/132/133 Series Maximum Clamping Force Force Range Maximum Diameter (Ref) Power Disc Device Crossbar Stud Centerline to Centerline Dimension 800 lbs (362.9 kg) - 2,000 lbs (907.2 kg) 3,000 lbs (1,360.8 kg) and 5,000 lbs (2,268.0 kg) 1,000 lbs (453.6 kg) - 6,000 lbs (2,721.6 kg) 1,000 lbs (453.6 kg) - 6,000 lbs (2,721.6 kg) 2,000 lbs (907.2 kg) - 10,000 lbs (4,535.9 kg) 8,000 lbs (3,628.8 kg) - 16,000 lbs (7,257.5 kg) High-Performance Press Pack Heat Sinks 2.25 in. (57.2 mm) 3.50 in. (88.9 mm) 3.50 in. (88.9 mm) 4.00 in. (101.6 mm) 4.50 in. (114.3 mm) 5.25 in. (133.4 mm) 2.750 in. (69.9 mm) Ref 4.000 in. (101.6 mm) Ref 4.000 in. (101.6 mm) Ref 4.625 in. (117.5 mm) Ref 5.500 in. (139.7 mm) Ref 6.000 in. (152.4 mm) Ref These high-quality mounting clamp assemblies are the worldwide standard for mounting, compression, and clamping press-pack SCR, thyristor, rectifier, and other high power disc packaged devices utilized in power distribution equipment, industrial controls, transportation systems, and power supply and conversion systems. Max SCR DIA Clamp assemblies will accommodate devices with overall case diameters to 5.25 in. (133.4 mm) maximum. Vertical device mounting space available for assemblies is determined by selecting an appropriate series crossbar by length which, when a series spring assembly is selected (based on maximum clamping force required), will provide the necessary vertical clearance space. For the 130 and 139 Series, this determination is made by subtracting the chosen spring assembly “Z” dimension (refer to dimensional tables) from the crossbar assembly “X” dimension minimum and maximum values, to calculate the available device mounting space clearance for the particular assembly combination. Spring assembly “Z” dimension is the dimension measured from the spring assembly device mounting surface to the spring assembly top surface. Some series have fixed dimensions for alpha characters. All spring assemblies are designed with a force indicator gauge. 130 SERIES Clamp Series Force Range Extrusion Profile 101.6 mm ALL 800 - 16000 LBS XX7151 84 mm ALL 800 - 16000 LBS XX6351 63 mm ALL 144 143 144 144 143 143 143 143 800 - 16000 LBS 800 - 6000 LBS 800 - 6000 LBS 800 - 6000 LBS 800 - 6000 LBS 800 - 6000 LBS 800 - 6000 LBS 800 - 6000 LBS 800 - 6000 LBS XX5735 XX5360 XX10239 O16235 O14442 XX3529 XX5730 O14191 XX3849 143 143 143 143 143 143 143 143 143 143 143 143 800 - 6000 LBS 800 - 6000 LBS 800 - 6000 LBS 800 - 6000 LBS 800 - 6000 LBS 800 - 6000 LBS 800 - 6000 LBS 800 - 6000 LBS 800 - 6000 LBS 800 - 6000 LBS 800 - 6000 LBS 800 - 6000 LBS XX5733 XX3559-2 XX5736 XX3561-2 XX5732 XX5731 XX3560-2 O13450 XX4554 XX5331 OO3537 XX5306 143 800 - 6000 LBS O14779 50 mm 40 mm COMPRESSION MOUNTING CLAMP ASSEMBLIES FOR SEMICONDUCTORS TO 2.25 IN. (57.2 MM) DIAMETER 130 SERIES SPRING ASSEMBLY Model No. No. of Leaves 130-1 130-2 130-3 130-4 130-5 2 2 3 4 5 “Z” Dim. in. (mm) 0.90 (22.9)   0.50 (12.7)    0.61 (15.5)   0.72 (18.3)   0.83 (21.1) Max Force lb. (kg) Weight lbs. (gms) 2,000 (907.2) 800 (362.8) 1,200 (544.3) 1,600 (727.8) 2,000 (907.2) 0.331 (150.14) 0.19 (86.18) 0.219 (99.34) 0.333 (151.05) 0.408 (185.07) 139 SERIES NOTES: 1. Spring assemblies are stainless steel leaves with a force indicator gauge, except the lowest cost Type 130-1 spring assembly manufactured from automotive grade stainless steel. Order Guide: Order Crossbar and Spring Assembly separately by type number from table. 130 SERIES CROSSBAR 800 lb - 2,000 lb (362.8 kg - 907.2 kg) Dimensions: in. (mm) lb. (kg) COMPRESSION MOUNTING CLAMP ASSEMBLIES FOR SEMICONDUCTORS TO 3.50 IN. (88.9 MM) DIAMETER 139 SERIES CROSSBAR 3,000 lb - 5,000 lb, (1,360.8 kg - 2,268.0 kg), Crossbar Device Mounting, Surface to Spring Assembly, Top Surface Dimension 139-3 SERIES CROSSBAR - 3,000 LB (1,360.8) “X” Dimension Model Min Max No. in. (mm) in. (mm) Weight lbs. (grams) 139-5 SERIES CROSSBAR - 5,000 LB (2,268.0) Model No. “X” Dimension Min Max in. (mm) in. (mm) 139-3A 139-3B 139-3C 139-3D 139-3E 1.52 (38.6) 1.83 (46.5) 2.14 (54.4) 2.45 (62.2) 2.77 (70.4) 1.89 (48.0) 2.21 (56.1) 2.52 (64.0) 2.83 (71.9) 3.14 (79.8) 0.689 (312.52) 0.7 (317.51) 0.706 (320.24) 0.721 (327.04) 0.732 (332.03) 139-5A 139-5B 139-5C 139-5D 139-5E 1.52 (38.6) 1.83 (46.5) 2.14 (54.4) 2.45 (62.2) 2.77 (70.4) 139-3F 139-3G 139-3H 130-3J 139-3K 3.08 (78.2) 3.39 (86.1) 3.70 (94.0) 4.01 (101.9 4.33 (110.0) 3.45 (87.6) 3.77 (95.8) 4.08 (103.6) 4.39 (111.5) 4.70 (119.4) 0.741(336.11) 0.762 (345.64) 0.773 (350.63) 0.784 (355.62) 0.79 (358.34) 139-5F 139-5G 139-5H 139-5J 139-5K 3.08 (78.2) 3.39 (86.1) 3.70 (94.0) 4.33 (101.9) 4.33 (110.0) 139-3L 139-3M 139-3N 139-3P 4.64 (117.9) 4.95 (125.7) 5.26 (133.6) 5.57 (141.5) 5.01 (127.3) 0.793 (359.70) 5.33 (135.4) 0.796 (361.06) 5.64 (143.3) 0.832 (377.39) 5.95 (151.1) 0.838 (380.11) 139-5L 139-5M 139-5N 139-5P 4.64 (117.9) 4.95 (125.7) 5.26 (133.6) 5.57 (141.5) Series Number 139-3 139-5 Height “A” Reference in. (mm) Width “B” Reference in. (mm) 0.72 (18.3) 1.02 (25.9) 0.95 (24.1) 0.83 (21.1) MECHANICAL DIMENSIONS MECHANICAL DIMENSIONS Dimensions: in. (mm) Dimensions: in. (mm) Weight lbs. (grams) 1.89 (48.0) 2.21 (56.1) 2.52 (64.0) 2.83 (71.9) 3.14 (79.8) 0.94 (426.38) 0.96 (435.45) 0.98 (444.52) 1.01 (458.13) 1.02 (462.66) 3.45 (87.6) 3.77 (95.8) 4.08 (103.6) 4.39 (111.5) 4.70 (119.4) 1.033 (468.56) 1.053 (477.63) 1.074 (487.64) 1.064 (482.62) 1.075 (487.61) 5.01 (127.3) 5.33 (135.4) 5.64 (143.3) 5.95 (151.1) 1.088 (493.51) 1.102 (499.86) 1.11 (503.49) 1.171 (531.16) 139 SERIES SPRING ASSEMBLY CROSSBAR HEIGHT AND WIDTH COMPRESSION MOUNTING CLAMP ASSEMBLIES FOR SEMICONDUCTORS TO 2.25 IN. (57.2 MM) DIAMETER 130 SERIES Model Number 139-1 139-2 Number of Leaves “Z” Dimension in. (mm) Maximum Force lb. (kg) 1 2 0.87(22.1) 1.25(31.8) 3,000 (1,360.8) 5,000 (2,268.0) Order Guide: Order Crossbar and Spring Assembly separately by type number from table. Dimensions: in. (mm) lb. (kg) Crossbar Device Mounting, Surface to Spring Assembly Top Surface Dimension “X” Dimension Model Min. Max. No. in. (mm) in. (mm) 116 Weight lbs. (grams) 130-A 130-B 130-C 130-D 130-E 1.74 (44.2) 2.05 (52.1) 2.36 (59.9) 2.67 (67.8) 2.98 (75.7) 2.12 (53.8) 2.43 (61.7) 2.74 (69.6) 3.05 (77.5) 3.36 (85.3) 0.4 (181.44) 0.418 (189.60) 0.427 (193.68) 0.437 (198.22) 0.447 (202.76) 130-F 130-G 130-H 130-J 130-K 3.29 (83.6) 3.60 (91.4) 3.91 (99.3) 4.22 (107.2) 4.53 (115.1) 3.67 (93.2) 3.98 (101.1) 4.29 (109.0) 4.60 (116.8) 4.91 (124.7) 0.461 (209.11) 0.476 (215.91) 0.486 (220.45) 0.497 (225.44) 0.51 (231.33) 130-L 130-M 130-N 130-P 4.34 (122.9) 5.15 (130.8) 5.46 (138.7) 5.77 (146.6) 5.22 (132.6) 5.53 (140.5) 5.84 (147.3) 6.15 (156.2) 0.52 (235.87) 0.534 (242.22) 0.544 (246.75) 0.559 (253.56) 117 PRECISION CLAMP HEAT SINKS PRECISION CLAMP HEAT SINKS PRECISION COMPRESSION MOUNTING CLAMP SYSTEMS 143 SERIES COMPRESSION MOUNTING CLAMP ASSEMBLIES FOR SEMICONDUCTORS TO 4.00 IN. (101.6 MM) DIAMETER COMPRESSION MOUNTING CLAMP ASSEMBLIES FOR SEMICONDUCTORS TO 3.50 IN. (88.9 MM) DIAMETER 143 SERIES CROSSBAR 2,000 lb - 6,000 lb (907.2 kg - 2,721.6 kg) 144 SERIES CROSSBAR 1,000 lb - 6,000 lb (453.6 kg - 2,721.6 kg) Crossbar Device Mounting, Surface to Spring Assembly, Top Surface Dimension Crossbar Device Mounting, Surface to Spring Assembly Top Surface Dimension “X” Dimension Model Min Max Weight No. in. (mm) in. (mm) lbs. (grams) Model No. “X” Dimension Min Max in. (mm) in. (mm) 143-A 143-B 143-C 143-D 143-E 1.30 (33.0) 1.86 (45.7) 2.30 (58.4) 2.80 (71.1) 3.30 (83.8) 143-F 143-G 143-H 143-J 143-K 143-L Overall Height “H” in. (mm) Weight lbs. (grams) 1.80 (45.7) 2.30 (58.4) 2.80 (71.1) 3.30 (83.8) 3.80 (96.5) 4.68 (118.9) 5.18 (131.6) 5.68 (144.3) 6.18 (157.0) 6.68 (169.7) 1.100 (498.95) 1.125 (510.29) 1.150 (521.63) 1.175 (532.97) 1.200 (544.31) 3.80 (96.5) 4.30 (109.2) 4.80 (121.9) 4.30 (109.2) 4.80 (121.9) 5.30 (134.6) 7.18 (182.4) 1.68 (195.1) 8.18 (207.8) 1.225 (555.65) 1.250 (566.99) 1.275 (578.33) 5.30 (134.6) 5.80 (147.3) 6.30 (160.0) 5.80 (147.3) 6.30 (160.0) 6.80 (172.7) 8.68 (220.5) 9.18 (233.2) 9.68 (245.9) 1.300 (589.67) 1.325 (601.00) 1.350 (612.35) 143 SERIES SPRING ASSEMBLY Model Number of Number Leaves Max. Clamping Force lb. (kg) Weight lb. (grams) 143-2 6,000 (2,721.6) 0.813 (368.77) 2 Order Guide: Order Crossbar and Spring Assembly separately by type number from table. 144-A 144-B 144-C 144-D 144-E 1.50 (38.1) 2.00 (50.8) 2.50 (63.5) 3.00 (76.2) 3.50 (88.9) 2.00 (50.8) 2.50 (63.5) 3.00 (63.5) 3.50 (88.9) 4.00 (101.6) 144 SERIES MECHANICAL DIMENSIONS 1.231 (558.37) 1.262 (572.43) 1.285 (582.87) 1.310 (594.21) 1.352 (613.26) 144 SERIES SPRING ASSEMBLY Model No. Clamping Force Range lb. (kg) Weight lbs. (grams) 144-2 1,000 (453.6) – 6,000 (2,721) 1.772 (803.77) Order Guide: Order Crossbar and Spring Assembly separately by type number from table. D imensions: in. (mm) lb. (kg) Dimensions: in. (mm) lb. (kg) 145 SERIES Dimensions: in. (mm) COMPRESSION MOUNTING CLAMP ASSEMBLIES FOR SEMICONDUCTORS TO 4.50 IN. (114.3 MM) DIAMETER MECHANICAL DIMENSIONS MECHANICAL DIMENSIONS 145 SERIES CROSSBAR 2,000 lb - 10,000 lb (907.2 kg - 4,535.9 kg) Crossbar Device Mounting, Surface to Spring Assembly, Top Surface Dimension “X” Dimension Overall Model Min Max Height “H” Weight No. in. (mm) in. (mm) in. (mm) lbs. (grams) 145-A 145-B 145-C 145-D 145-E 145-F 1.75 (44.5) ­ 2.50 (63.5) 3.25 (82.6) 4.00 (101.6) 4.75 (120.7) 5.50 (139.7) 2.50 (63.5) 3.25 (82.6) 4.00 (101.6) 4.75 (120.7) 5.50 (139.7) 6.25 (158.8) 6.00 (152.4) 6.75 (171.5) 7.50 (190.5) 8.25 (209.6) 9.00 (228.6) 9.75 (247.7) 3.845 (1744.06) 3.987 (1808.47) 4.06 (1841.58) 4.187 (1899.19) 4.37 (1982.20) 4.459 (2022.57) 145 SERIES SPRING ASSEMBLY Model Clamping Force Range No. lb. (kg) 145-2 2,000 (907.2) – 10,000 (4,535.9) Weight lbs. (grams) 2.01 (911.72) Order Guide: Dimensions: Order Crossbar and Spring Assembly in. (mm) separately by type number from table. lb. (kg) Dimensions: in. (mm) Dimensions: in. (mm) wakefield-vette.com 118 Contact us: (603) 635-2800 119 PRECISION CLAMP HEAT SINKS PRECISION CLAMP HEAT SINKS PRECISION COMPRESSION MOUNTING CLAMP SYSTEMS COMPRESSION MOUNTING CLAMP ASSEMBLIES FOR SEMICONDUCTORS TO 5.25 IN. (133.5 MM) DIAMETER 146 SERIES MECHANICAL DIMENSIONS 132 & 133 SERIES 132 SERIES 133 SERIES NATURAL AND FORCED CONVECTION CHARACTERISTICS NATURAL AND FORCED CONVECTION CHARACTERISTICS 146 SERIES CROSSBAR 8,000 lb -16,000 lb (3,628.7 kg - 7,257.4 kg) Crossbar Device Mounting, Surface to Spring Assembly, Top Surface Dimension “X” Dimension Overall Model Min Max Height “H” Weight No. in. (mm) in. (mm) in. (mm) lbs. (grams) 146-A 146-B 146-C 146-D 146-E 146-F 146-G 1.54 (39.1) 2.29 (58.2) 3.04 (77.2) 3.79 (96.3) 4.54 (115.3) 5.29 (134.4) 6.04 (153.4) 2.29 (58.2) 3.04 (77.2) 3.79 (96.3) 4.54 (115.3) 5.29 (134.4) 6.04 (153.4) 6.79 (172.5) 5.92 (150.4) 6.67 (169.4)  7.42 (188.5)  8.17 (207,5)  8.92 (226.6)  9.67 (245.6) 10.42 (264.7) 3.813 (1729.55) 3.938 (1786.25) 4.063 (1842.95) 4.188 (1899.64) 4.313 (1956.34) 4.438 (2013.04) 4.563 (2069.74) MECHANICAL DIMENSIONS 132 SERIES (EXTRUSION PROFILE 3560-2) 146 SERIES SPRING ASSEMBLY Model Number 146-2 Number of Leaves 2 Clamping Force Range lb. (kg) Maximum Force lb. (grams) 8,000 (3,628.7) - 16,000 (7,257.5) 2,688 (1,219.26) Order Guide: Dimensions: Order Crossbar and Spring Assembly in. (mm) separately by type number from table. lb. (kg) MECHANICAL DIMENSIONS 133 SERIES (EXTRUSION PROFILE 3559-2) Dimensions: in. (mm) 132/133 SERIES HIGH-PERFORMANCE HEAT SINKS FOR COMPRESSION TYPE DEVICES Series **132-4.5 **132-10 **132-15.5 **132-5-9 **132-11-9 Series **133-4.5 **133-7.5 **133-10 **133-5-9 **133-7.5-9 **133-11-9 Dimensions: in. (mm) 132 & 133 SERIES Thermal Performance at Typical Load (2) Standard P/N Nominal Dimensions: (1) Clamp Natural Convection Black Gold Width Length “A” Height System Convection (°C/W) @ Anodize (4, 5) Iridite in. (mm) in. (mm) in. (mm) Series (5) (°C/W) (3) 500 LFM) 132-4.5B 132-10B 132-15.5B 132-5-B9 132-11-B9 133-4.5B 133-7.5B 133-10B 133-5-B9 133-7.5-B9 133-11-B9 132-4.5G 132-10G 132-15.5G 132-5-G9 132-11-G9 133-4.5G 133-7.5G 133-10G 133-5-G9 133-7.5-G9 133-11-G9 5.000 (127.0) 5.000 (127.0) 5.000 (127.0) 5.000 (127.0) 5.000 (127.0) 7.000 (139.2) 7.000 (139.2) 7.000 (139.2) 7.000 (139.2) 7.000 (139.2) 7.000 (139.2) 4.500 (114.3) 10.000 (254.0) 15.500 (393.7)  5.000 (127.0) 11.000 (299.4)  4.500 (114.3)  7.500 (190.5) 10.000 (254.0) 5.000 (127.0)   7.500 (190.5) 11.000 (279.4) 2.250 (57.2) 2.250 (57.2) 2.250 (57.2) 2.250 (57.2) 2.250 (57.2) 3.125 (79.4) 3.125 (79.4) 3.125 (79.4) 3.125 (79.4) 3.125 (79.4) 3.125 (79.4) Material: Aluminum, Black Anodized Finish: B = Black Anodized, G = Gold Iridite 0.61 0.38 0.28 0.61 0.37 0.37 0.28 0.26 0.37 0.28 0.24 Type 0.170 0.130 0.100 0.170 0.120 0.110 0.085 0.082 0.110 0.085 0.076 Use with 132-4.5 132-10 132-15.5 133-4.5 133-7.5 133-10 132-5-9** 132-11-9** 133-5-9** 133-7.5-9** 133-11-9** ** wakefield-vette.com 120 130 130 130 139 139 130 130 130 139 139 139 MULTIPLE ASSEMBLY CONFIGURATION – 2 ea 132-4.5 3 ea 132-4.5 – – 2 ea 133-4.5 – 2 ea 132-5-9 – – 2 ea 133-5-9 A 2.25 2.25 – – 2.25 – 2.50 – – 2.50 B 5.50 5.50 5.50 6.00 6.00 C D See Fig.132 – 10.0 5.50 15.5 See Fig.133 See Fig.133 – 10.0 See Fig.132 - 11.00 See Fig. 133 See Fig. 133 – 11.00 -9 indicates heat sinks drilled for 139 clamp. NOTES: 1. Nominal dimensions for one heat sink of this type. 2. Thermal performance values shown are per pair of heat sinks. 3. Natural convection performance at 50°C heat sink rise above ambient. 4. Black anodize finish [1.875 in. (47.6 mm) diameter spot face. Device mounting surface area free of finish]. 5. Predrilled heat sinks accept 130 and 139 Series clamp systems. Contact us: (603) 635-2800 121 Precision Clamps and Heat Sink Assemblies Clamp Assembly Procedure All illustrations assume the following parts: 143 series crossbar, 143-2 spring leaf assembly and one or two 132-5-B9 heat sinks, compression SCR (not a Wakefield product), EJC No. 2 thermal joint compound (not a Wakefield product). Wakefield recommends using two heat sinks, one on each side of the SCR. When received, the top edges of the force indicator should be in line with bottom edge of the spring leaf as shown below. This is the zero position. If this is not the case, move it to zero with your hands or a pair of pliers. Too low Too high Proper zero position If using one heat sink only: The roll pin will need to be adjusted to fit into the blind hole of the SCR. Check the depth of the blind hole and allow a clearance of at least 0.025 in (0.65 mm). Care will be needed to ensure that the upper retaining washer is held against the top leaf spring. Keep washer fixed as shown Roll pin ≤ (SCR hole depth - 0.025”) www.wakefield-vette.com Precision Clamps and Heat Sink Assemblies Clamp Assembly Procedure If using two heat sinks on both sides of the component: place the heat sink on a flat surface and put the leaf spring assembly between the fins on center with the roll pin into the hole. With a hammer drive the pin into the hole and through the heat sink, so that the pin comes through the other side and protrudes 0.050 in (1.3 mm). This is helpful in indexing the SCR to keep it concentric to the forces applied when the nuts are tightened. This also holds the spring leaf assembly in place. 0.05” Apply a non-silicone based thermal compound to the spotface of the heat sink without the spring leaf assembly/roll pin. It is recommended that Electrical Joint Compound No. 2 (EJC #2) be used, as it contains a fluoride compound that removes the surface oxides on both the heat sink surface and the pole face of the SCR. Do not use Wakefield Type 120 compound, as it will cause a hot spot at this joint. There are many methods for applying the proper thickness of grease with full coverage and without excessive squeeze-out; this should be done by trial and error, removing the SCR and checking the amount of coverage. Electrical Joint Compound No. 2 (EJC #2) is supplied by: ACA Conductor Accessories www.acasolutions.com (800) 866-7385 Apply thermal joint compound to hatched area www.wakefield-vette.com Precision Clamps and Heat Sink Assemblies Clamp Assembly Procedure Apply the thermal compound to the spotface of the heat sink with the spring leaf assembly and place the SCR in position on the spotface, centering the SCR on the roll pin. At this time fit the crossbar studs between the two innermost fins and through the holes of the other heat sink (without the spring leaf assembly). Slowly drop the crossbar studs through the holes in the heat sink with the SCR and spring leaf assembly, making sure that the SCR fits over the spotface on the upper heat sink. Then flip the assembly upside down, supporting the crossbar against the inner surface of the heat sink. Drop the washers over the threaded ends of the studs, and then apply the nuts to the threads and screw on until finger tight. 2. Center SCR on pin 3. Drop second heat sink and crossbar assembly onto first heat sink 1. Apply thermal grease 5. While supporting crossbar, apply swivel washers and nuts 4. Flip assembly and support crossbar Precision Clamps and Heat Sink Assemblies Clamp Assembly Procedure Tighten the nuts alternately one-quarter turn each until you have reached the required force recommended for the SCR. This occurs when the edge of the marked step on the force indicator matches the bottom edge of the spring leaf as shown below. “4” lines up with bottom edge of spring leaf Æ 4000 lb on 6000 lb scale Additional notes: Avoid short cuts in assembling these components, as it is important that deflection of the spring leaf assembly be given precedence over all other choices of force measuring techniques. Do not use torque wrenches to set the force level, as torque is not a measure of force on these assemblies. The lubricants and surfaces of the nuts and washers will vary and cause a gross misrepresentation of force if torque is used as a force indicator. Spotfaces are machined to a minimum depth to provide a flat surface for the SCR to sit on. The pole face of the SCR is only about 0.060 in (1.5 mm) above the surrounding bellows ring that is bonded to the SCR porcelain housing. The pole faces of the SCR deflect slightly as the force is applied to make contact to the silicon dioxide disc inside. If the spotface is too deep on the heat sink, the shoulder of the bellows will make contact to the heat sink, and the proper force required at the pole faces will not be met. Every clamp/heat sink/SCR assembly will not have the same physical heat sink thicknesses to accommodate, and will require that the customer install small pins into the heat sinks to index the SCRs. The pins in the leaf spring assemblies will not be long enough in most cases and cannot be driven through the thicker heat sinks. In these applications the pin is driven into the heat sink a minimum distance to lock the leaf spring assembly to the heat sink.