Projection Welding Systems - Pyramid Engineering

Precision Welding Systems

The techniques of welding are still widely considered a black art by many people, and who can blame them, when the simplest form of welding is the blacksmith's forge and hammer. With many years of industry experience the Pyramid Engineering Services team of engineers have taken high precision welding to its ultimate form. Our wide application knowledge and extensive experience allows us to select, from a wide range, the most cost effective system to satisfy your welding requirements. The modular ACW &. DCW Series of high precision welding systems offer both AC and DC welding together with a choice of operational modes. Complete production cells are offered by the careful selection of standard options, accessories and associated product ranges. This range offers some of the most noticeable benefits in the industry due to:-

• • • • • • • • • •

Modular design, to allow maximum flexibility as requirements change, with good operator and maintenance access. Closed loop monitoring options to maintain optimum conditions. Manual, Rotary Table or Inline magazine operation with production rates from 250 to 10,000 units per hour. Pneumatic or hydraulic operation allowing complete device ranges to be covered. Synchronous AC or Capacitron discharge DC power supplies. Positive datum machining to allow accurate alignment and interchangeability of tooling and wear parts. Laser, Seam and Cold welding alternatives for special package arrangements available. Sealing rates better than 1 x 10-9 mbar 1-1 Site service and back up. One year guarantee.

Welding heads are of a three-tiered die-set construction designed for rigidity and long life accuracy. The unique design incorporates cast steel base and large diameter hardened and ground columns, which ensure that when the head operates there are little or no forces acting to cause bending moments during the applied welding pressure. A low inertia aluminium middle platen carries the top electrode and by the use of a series of stored energy springs, provides fast follow-through during the mastic weld phase. Once set this gives absolute consistent repeatability. The top plate carries a cylinder which acts as a prime actuator to close the electrodes and build up energy in the die springs for weld follow-through. An option of either pneumatic or hydraulic operation can be provided.

WH2 manual welding head One of the main applications for the ACW & DCW Series of high precision welders is the hermetic sealing of metal package semiconductor devices for the electronics industry. Other examples of the successful use have been in the sealing of Lithium Battery cases, Metal Relays and Barometric Transducers. A welding system normally comprises a number of integrated assemblies including power supply, welding head and handling system. Although the physical demands of the package directly determine the choice of welding head a number of considerations affect the choice of the welding power supply. A major factor is often the capacity of the available electrical supply since AC welding requires considerable higher current than the DC stored energy system. Other less apparent factors can determine the finished quality of the encapsulated device. In welding critical components the DC stored energy system with its fast heat phase prevents metal vaporization and minimises local heating of the welded product.

WH4 Inline welding head

Rotary table electrodes

Electrode faces are fine surface ground to ensure flatness and mate directly to the high conductivity copper platens; mounted onto the die-set tiers, which connect through leaf roll flexible straps to the secondary winding of the welding transformer. A dowel spigot is used to locate the electrodes and a quick turn lock ring clamps it directly onto its secondary connection. Alignment over 25mm is better than 15 microns, not once but every time you weld. These same high quality production techniques are used to produce multiple position rotary tables or inline magazine index systems, allowing higher production rates to be achieved. The pitch of these electrodes is made to be compatible with other handling systems that may already be in use in the production process. Electrodes are available in various forms, either as basic blanks or fully machined to suit your particular component.

The principle of AC or Synchronous welding is to use an electronic switch, in our case two inverse parallel connected thyristors, which apply a number of mains cycles directly to the primary of a welding transformer. A solid state controller allows selection of the number of cycles applied and the degree of conduction for that cycle(s), thus controlling the total amount of power applied to the weld. Our standard weld controller offers pulse selection from 1/2 to 10 Hz with adjustment of the conduction from 2 to 97% of the cycle time. The controller is used in conjunction with a range of high efficiency "C" core welding transformers, specially designed with fast recovery, to allow use on 1/2 cycle pulsing. Water cooling can be fitted to both welding transformer and thyristor switch.

AC Welding block diagram

Typical welding waveforms Because of their high speed mode of operation Synchronous controllers are often used on automatic rotary or inline welding applications where fast welding rates preclude the use of slower DC Capacitron discharge power supplies. With a selection of transformers from 50 KVA to 150 KVA most semiconductor devices from TO 18 to TO 3 size outlines can be welded. Above this size the power requirements for synchronous welding are tremendous and the use of DC power supplies are recommended. With a range from 1000 to 20,000 Joules almost any device can be welded from small crystal packages to large hockey puck SCR devices. With its narrower energy pulse the DC Capacitron discharge also offers many advantages in the actual characteristics of the weld, over that of the synchronous system. A typical comparison is shown on the graph.

DC or Capacitron discharge welding is unique in both its mode of operation and the resultant weld characteristics. The controller's basic functions, as shown in the block diagram, are to take a relatively small mains supply, rectify it and charge a series of capacitors to a pre-set, closed loop controlled voltage level. The controller allows adjustment of the charge voltage to alter the welding energy which is created by discharging the stored energy via an electronic switch into the primary of the welding transformer. Typically 70% of the energy is dissipated within 4 milliseconds, the remaining low power tailing off and doing little work. The principle of operation and the design of the circuit isolates the weld discharge from the mains supply thus giving constant weld pulses irrespective of any mains fluctuations. Another important feature with this system is that no feedback of welding "spikes" into the mains supply occurs.

DC Welding block diagram

DCW weld sequence controller Although the actual production process is to weld a particular package the encapsulation process is often complicated by the requirement to seal under certain atmospheric conditions. An encapsulation suite normally comprises three integrated sections which are designed to interconnect to form an integrated production cell with similarity of design concept and operation. We offer a complete range of modular gloveboxes, airlocks and vacuum pre bake ovens to allow system building to suit your own production requirements, with the use of carefully selected options to achieve the highest of production standards.

Our welding systems are built together with all associated controls and power supplies into a solid square section clad aluminium frame with a solid base to ensure stability and mechanical alignment. Capacitron power supplies and hydraulic drive packages are housed in similar cases which stand adjacent to the main welding machine. All welding systems are controlled using a PLC (Programmable Logic Controller), which drives the weld head cylinder, times the pre (squeeze), post (hold), off weld dwells and initiates the actual weld pulse. On rotary table and inline welding systems it also controls all auxiliary functions such as index, transfer and component eject mechanisms. In addition to the actual weld power controls the weld controller panel incorporates system status indicators, squeeze, hold and off dwell timers which are adjustable from 0.1 to 1.0 second.

AC welding control console Diode crimp and seal unit Typical welding suites will be made up of entry/exit airlock, welding glovebox, vacuum unloading/storage glovebox and vacuum bake oven.

As the encapsulation of electronic devices falls into several categories one of the prime considerations is the level of automation required, this being dependent on production schedules, number of available hours worked, labour and payback cost. With a basic manual single operation welder being capable of producing up to *400 units per hour we offer two further steps to increase output. Firstly, multi position rotary table, (normally 8 or 12), which allows production rates of up to *2,200 UPH. Secondly, inline multi position magazine feeds, (normally 10, 33 or 52), which allow production rates of *7,500 UPH with up to *10,000 UPH possible under certain conditions. Automatic feed conveyor, pneumatic transfers, component pick & place units and handling fixtures are added to our systems as required to offer you, the user, the most economic solution to your production requirements. * Based on the components to be welded, handling system employed and operator capability.

Typical welding suite

Under certain specialised conditions it may be necessary or advantageous to encapsulate packages either under special conditions or by different welding techniques. Alternatives which we can supply include: •

Parallel gap seam welding which offers the ability to stitch weld a variety of flat lid hybrid packages, by use of a continuous movement under rotating roller electrodes.

•

Cold welding die-sets which utilise high pressures to form the molecular bond.

•

Pulsed YAG Laser welding connected by fibre optic cables to the working area within a glovebox allowing many different materials and package shapes to be welded.

Cold Welding head and devices The welding systems outlined in this publication can boast a long and proven field record with design principles going back over some 35 years. This proven record has offered many of the world's users of encapsulation equipment countless benefits both in terms of operating efficiency and high quality yields. Pyramid Engineering Services provide a full back up of spare parts, site survey, site installation and service on this equipment. We believe in providing you, the user, with a better product for the way forward. Providing the opportunity to gain:• • • •

•

Higher yields and improved productivity of your process. Closer production controls of your process. Lower running costs for your product line. Long lasting high quality equipment for your capital outlay. Equipment that you and your company or organisation will be pleased that you purchased from Pyramid Engineering Services.

Typical welded devices Our range of welded packages is forever growing as the industry's requirements change and new applications are developed. A sample of the most common packages welded are listed below with some also shown in the above array. •

Transistor device packages

•

Power device packages

•

Crystal device packages

• •

Hybrid device packages Special device packages

TO 18, 72, 5, 39, 8, 66 & 3 DO4, 5, EI2, I4, I5, & Pucks UM 1, HC 49, 45, 18, 6, DIL 4 & ½ DIL DIL I4, 16, 24 TO 220, Quad packs, m/wave diode

SPECIFICATIONS Weld head specification Physical Data Electrode Dia. Standard Maximum Special Parallelism Head Stroke Maximum Column Centres

Head Option for Machine size

Units

WH1

WH2

WH3

WH4

mm mm mm μm

25 32 45 10

38 50 65 15

63 63 80 20

10 15 25 10

mm mm

60 120

75 170

85 180

25 210

1425 100

3765 263

3765 263

-

496 132

1112 296

-

496 132

Weld Pressure (Bar) Hydraulic @69 Max Kgf @5 Min Kgf Pneumatic @6 Max Kgf @0.7 Min Kgf

WH1

WH2

WH3

WH4

ACW 50 ACW 100 ACW 150

Std Std -

Opt Std

Opt

Auto Auto Auto

DCW 1000 DCW 3000 DCW 6000 DCW 10000 DCW 12500 DCW 15000 & 20000

Std Std -

Opt Std Std -

Opt Opt Std Ext 1

Auto Auto Auto -

Notes: 1. 2. 3. 4.

WH3 Hydraulic, WH4 Pneumatic only. Std. Fitted as standard. Opt. Fitted optionally Ext 1 115mm Extended version of WH3 fitted 32mm Extended version available on WH1 & WH2 Auto. Only fitted to inline feed systems

5.

Weld Machine specification Power supply DCW/ACW

Units

1KJ

3KJ

6KJ

10KJ

12.5KJ 15KJ

20KJ

Max. Energy . Min. Energy Capacitance Time Range Phase Shift Transformer Rating Nominal Rating Max. Sec Rating Welds/min @ max Voltage 3φ Frequency Current per φ Water Cooling @ 16°

J J μF Hz %

1024 64 400

3037 96 1200

6075 192 2400

10125 320 4000

12656 400 5000

20250 640 8000

KJ KVA KVA V Hz A l/min

CD25 3.0

CD25 3.0

CD75 8.5

15187 480 6000

/

CD150 CD150 CD200 CD200 16.0 16.0 22.0 22.0

50K

100K

SW10

½ to 10 2 to 97 SW25 SW75

50 155 170

50 40 30 20 20 16 12 -------- 380/440 (or 460/480 with use of transformer) ------------------------------------ 50/60 ----------------------------------30 30 30 60 60 60 60 2 2 2 2 2 2 2

150K

60 5

100 150 310 460 @ 1 cycle 50 or 60 50 or 60 120 180 5 5

50K

100K

* *

* *

Welding machine selection for common package sizes

Hybrid

Notes: 1. 2.

* *

*< *< * * *>

UM I HC 49 45 18 6 ½ DIL DIL 4

* * * * *

DIL 14 DIL 16 DIL 24

* * * * * *

*< * *

10KJ

12.5KJ 15KJ

*
Top end of range: *< Bottom end of range: Sometimes alternative or hybrid machines are selected to cover a range of packages.

Pyramid Engineering Services Co. Ltd 25 Hailey Road, Hailey Road Business Park, Erith, Kent DA18 4AA. United Kingdom Tel +44 (0)208 320 9590 Web www.pyramideng.com Fax +44 (0)208 311 2567 Email [email protected]