Metal working – Means to assemble or disassemble – Means to assemble electrical device
Patent
1986-09-17
1988-03-01
Echols, P. W.
Metal working
Means to assemble or disassemble
Means to assemble electrical device
29593, 29712, 29759, B23P 1904
Patent
active
047276452
DESCRIPTION:
BRIEF SUMMARY
THE OBJECTS OF THE INVENTION AND ITS MOST SIGNIFICANT CHARACTERISTICS
Pick and place machines for surface mounting of electronic components fetch the components from a magazine and place them on a substrate, e.g. in the form of a printed circuit board. The present invention relates to an apparatus which at low price provides a number of advantageous properties in a pick and place machine, viz.:
mounting of component with extremely varying size, e.g. from 2.times.1.2 mm to 34.times.34 mm without change of centering tool
centering of the component relative to the housing
centering of the component relative to the connecting leads
mechanical measurement of the component housing
mechanical measurement of the distances between the external connecting leads of the component
connection of the leads to a test equipment to measure its electrical properties, and
centering and measurement of mechanical and electrical properties concurrently with the movement of the component which means without time loss under normal conditions.
THE BACKGROUND OF THE INVENTION AND PRESENT PROBLEMS
Mounting of surface mounted components involves a number of problems compared to the old technique of mounting components, the leads of which are mounted in holes. These problems are as follows:
(1) The components are placed on a surface. The mounting error will therefore be continuously variable which leads to boundary problems between acceptable and unacceptable mounting. The old art components have a binary mounting error which means that either all leads are in their holes or they are not.
(2) There are different reasons for an increased interest to glue the components before soldering. This puts increased demands on the mounting position. Up till now the components have mostly been mounted on soldering paste. During the soldering operation surface tension phenomena will cause an automatic centering of the component. However, if the component is glued this centering effect will be eliminated.
(3) The components are small. The distance between the leads on a component old in the art is almost always 2.54 mm or more. For surface mounted components it is 1.27 or 0.80 mm and will decrease in the future.
(4) Machines for mounting of components old in the art utilize guiding holes which are drilled in the same operation as those in which the components should be mounted. The errors between the guide holes and the component holes will therefore be relatively insignificant.
(5) The components are so small that they mostly cannot be provided with identifying text. This increases the demand to measure the component electrically before mounting to ensure that the correct component will be mounted.
Items 1-4 above will together present great difficulties when mounting components with a lead distance of 1.27 mm and less by gluing. The enterprise Elektronikcentralen i Denmark which is well known in the Nordic countries has issued a study No. ECR-143 with the title "Leadless components" and in the fifth chapter, page 15, they have reached the conclusion that "from the present prerequisits the only solution now is to utilize manual mounting only and thereby introduce an optical correction of certain tolerances".
The actual Swedish production of surface mounted components with the lead distances 1.27 and 0,80 mm is often handmade even in the simpler case when the components are not glued.
Existing machines for surface mounting reflect the statements made above. These machines can be divided into different types, namely:
specialized machines which can only mount components having a size within very narrow limits, e.g. from 2.times.0.8 mm up til 3.2.times.2.0 mm. These machines often have high capacity and a high price.
Module machines are built up by a number of mounting stations each of which is specialized for a certain group of components of the same of almost the same size and design. Thus, a customer who uses many different component types must have a number of modules and will therefore have to pay a high price.
Machines without a centering ope
REFERENCES:
patent: 4151945 (1979-05-01), Ragard et al.
patent: 4286380 (1981-09-01), Blount
patent: 4417683 (1983-11-01), Lewis et al.
patent: 4557043 (1985-12-01), Starski
patent: 4610473 (1986-09-01), Hawkswell
"Komponentmontering"--Modern Elektronik, 11/9/84.
"Ytmonterar i automat"--Elektronik Medaktrell Electronik, 9/84.
"Mottagningskontroll Och Fortenning"--Medern Elektronik, 11/9/84.
"Surface Mounting Alters PC-Board Scene"--Electronic, 2/9/84.
Rodin Gunnar
Stridsberg Lennart
Echols P. W.
Mydata Automation AB
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