|
|
Laser Resistor Trimming
What is laser trimming?
Laser trimming is a way of achieving
precision adjustment of the attributes of an electronic circuit. A laser
removes material from the appropriate component and thus adjusts its
value. Laser trimming is faster, more economical and more accurate than
other methods such as select-on-test, using potentiometers or abrasive
trimming. A lateral cut into an SMD or hybrid resistor increases its
resistance. Removing part of the top electrode of a capacitor decreases
its capacitance. There are two fundamental types of laser trimming;
passive trimming is where a resistor or capacitor is trimmed to a
specific value. Active or functional trimming refers to
adjustment of a circuit parameter such as voltage, current or frequency.
For a more detailed technical explanation see the
Technology section
of this web site.
What is a laser trimmer?
A laser trimming system speeds up, automates and increases the accuracy
of your trim application. A laser trimming systems consists of (i) a
laser with a high beam quality and small beam diameter (20 to 40
microns) (ii) an industrial PC with software to develop applications
programs (iii) a galvanometer consisting of two mirrors which control
the beam movement (iv) instrumentation to measure the circuit parameter
(v) a prober may be used to make contact with the circuit and (vi) a
step & repeat table may be required to trim multiple circuits. LS
engineers build a system from modules, customised to your requirements,
providing optimum cost and performance. LS also supplies modules for
integration into OEM systems or production lines, as well as complete
stand-alone systems with instrumentation, prober and automated handling.
|
|
|
How does a laser trimming system work?
For trimming, the circuit board is placed under
the positioning unit and contacted electrically. The beam deflection unit moves the
laser beam to the component to be trimmed and trims it until the programmed
nominal value is reached. A lateral laser cut in a resistor narrows the current
flow path, thereby increasing the resistance. Removing part of the top electrode
of a capacitor decreases the capacitance. During the trim the relevant parameter
is measured continuously or sequentially via IEEE bus and compared with the
nominal value. When the parameter reaches the nominal value the trim cut stops
automatically. If the parameter cannot be measured
continuously the trim is done step by step. Resistance, voltage,
current, frequency - with suitable measuring equipment any output
parameter can be trimmed. Various types of cut and the appropriate selection of laser
parameters enable a precise trim of the circuit board, with excellent long-term
stability.
Examples of laser trim cuts on resistors and
capacitors |
|
'L' cut into a thick film resistor
|
'Serpentine' cut into a thick film resistor |
'Shave' cut
into smd capacitor |
|
Software
The LS software runs under Windows. The programs can be generated
flexibly in a flow chart. Simple, configurable interfaces permit the
seamless integration of external systems as well as the connection to
higher level host computers. Parameter and command items using
configurable dialog boxes facilitate programming and reduce programming
time.
Industrial laser systems for trimming resistors,
capacitors, hybrid and other electronic circuits |
