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The quality control of Hitech Electronic System products starts from basic raw material and continue right upto all stages of production down to finished product testing & even to final usage of where we extend services to our customer in the proper handling of the product.

Testing of raw material

  1. All electronic components such as resistors, capacitors, transistors, diodes, zener diodes, voltage regulator IC's, SCR's, op-amps, special purpose Ics, etc are checked for acceptance and are shifted to production department for actual usage.
  2. As these components are required in huge quantity, the method of sampling inspection is adapted. The sampling plan is as follows :
    Lot No. % for inspection Remark
    200 nos. 20 % Accept # rejection < 5%
    500 nos. 15 % Rejection > 5% => additional 10 % to be checked => overall rejection, 5% : accept the lot
    1000 nos. 10 % -----------do-----------

     

  3. Metallic / plastic enclosures are tested and checked for physical dimensions such as diameter, pitch, length, and other parameters at the suppliers site. Necessary gauges & dies are developed by Hitech Electronic System and kept at the vendors premises.
  4. The PCBs are subject to 100 % inspection for visual inspection such as track cracks, tinning, dimensions, shorting, etc. The track thickness is checked by thickness gauge. The track thickness should be minimum 8 microns.

To ensure minimum rejection at the final stage and best possible quality of product, inspection is carried out at various stages of manufacturing.

In-process Quality Control :

  1. Temperature test :
    All components are inserted and soldered on PCB. After this, the populated PCBs are checked for circuit working. The rejected populated PCBs are sent, for reworking PCBs are kept in laboratory oven @ 55oC for one hour and then tested for circuit working. The rejected PCBs are scrapped. The accepted PCBs are then sent for vibration test.

     
  2. Vibration test : PCBs are kept on vibration plate which vibrates at 50 Hz with 1 mm amplitude. This test help us to find out hidden dry solders and solder point cracks.

     
  3. Electrical / other parameter testing : Sensing distance with respect to supply voltage, No load current, maximum output current, short circuit protection, reverse polarity protection, etc is tested. 100 % inspection is carried out for above mentioned tests. At this stage depending upon specific requirement of customer, certain tests are carried out ; e.g. in certain applications customer may be requiring 25 % hysterisis as against standard 10 %. Such instructions are included in the job sheet prepared by the marketing engineer.

     
  4. Accepted PCBs are then sent to the potting area where PCBs are placed into the metallic/non-metallic housings. Depending upon the product potting is carried out These potted/unpotted products are then sent to final inspection stage and then to despatch department.

Finished good Inspection

Following tests are carried out in general. (Other tests are carried out depending upon specific requirement of customer). 

  1. No load current
  2. Output current
  3. Voltage test
  4. Hysterisis
  5. Sensing distance variation
  6. Short circuit protection
  7. Reverse polarity protection
  8. Cable colour code
  9. Physical dimensions
    Non confirming products are scraped immediately.

Accepted switches are then subjected to final heat run test. Here the switches are kept in ON condition for 3 hours, in OFF condition for 1 hour and again in ON condition for 3 hours.

The sampling plan is as follows :

  • upto 50 nos. => 25% random samples => 2 nos. rejected => additional 25 %
  • upto 100 nos. => 20 % random samples => 2 nos. rejected => additional => 20 %
  • More than 100 nos => 15% random samples => 2 nos. rejected => additional 10%

To avoid any delay in delivery schedule, due to final stage inspection : usually 5% more than the order quantity is taken for processing.

Note : Above mentioned tests, specifications varies with respect to the type of switch/product such as diameter, sensing distance, enclosure configuration, load technique, load logic, output load requirement, hysterisis, switching frequency etc.

 

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