A Division of General Electronic Devices
Manufacturer of Quartz Crystals, Oscillators and Filters
(760) 979-1441 • 320 South Pacific St., San Marcos, CA 92078
There are several areas where visual inspection, of hybrids, MCMs and RF and Microwave modules, is used to insure compliance to manufacturing processes and procedures and insure device quality and reliability. Table I show some of the typical checkpoints used to verify compliance to design documentation, process control and required customer specifications.
As part of incoming inspection, visual inspection is performed as part of the Element Evaluation which is used to verify that procured materials and devices meet their specified characteristics and are adequate to perform as intended under the conditions experienced in the application. There are two levels of visual inspection Class K (the more stringent requirements) and Class H.
This test is performed per MIL-STD-883 TM 2017 Internal Visual (HYBRID) on microelectronic devices prior to hermetic seal on a 100% inspection basis to detect and eliminate devices with internal defects that could lead to device failure in normal application. It may also be employed on a sampling basis prior to capping to determine the effectiveness of the manufacturers quality control and handling procedures.
Pre Cap Visual Inspection (Preseal) Criteria inspects the following items:
Defects related to wafer fab, saw and break, probe test etc.
Thick film/thin film substrate defects e.g., cracks, "chip outs"
Laser Trim defects
Epoxy die attach, fillet criteria for active and passive elements
Eutectic solder attach
Epoxy attach of chip capacitors and chip resistors
Wirebond defects, e.g., excessive squash out, heel cracks, misplaced bonds, etc. ball bonds, wedge bonds, ribbon bonds and heavy wedge aluminum
Foreign Material Identification and Contamination Control
Rework and Repair Limitations and all the associated traveler information and traceability information is checked and reviewed at this step in the process flow.
Pre Cap visual inspection magnification is 10 to 60X. Within the Pre Cap TM 2017 the requirements for high mag die inspect are also referenced, These high power inspections are typically accomplished as part of incoming inspection to screen out defects related to the wafer fab processing.
High power visual inspection magnification is 100X to 200X for Class K and 75X to 150X for Class H, higher mag levels are often need for microwave components due to their small feature sizes.
For GaAs devices the high power inspection levels are listed in Table II below.
TABLE II. GaAs microwave device high power magnification requirements
A low power visual inspection (~40X) reject is shown in Figure 1 showing conductive epoxy bridging adjacent gold conductor traces on thin film substrates.
Figure 2 is at high power (~400X) showing an open conductor and exposed passivation on a 1 micron GaAs integrated circuit.
Figure 1 Typical low power visual reject
Figure 2 High Power inspection of an Open Conductor on a GaAs integrated circuit.
The pre cap inspection is typical performed under a laminar flow hood to comply with TM2017 requirement of 100 (0.5 µ m or greater) particles/cubic foot controlled environment (class 5 of ISO 14644-1) for Class K (Class level S)
During the time interval between internal visual inspection and preparation for sealing, the devices are stored in a 1000 (0.5 µm or greater) particles/cubic foot controlled environment (class 6 of ISO 14644-1). Devices are in covered containers when transferred from one controlled environment to the sealer.
The purpose of this test method is to verify the workmanship of hermetically packaged devices and to inspect for damage due to handling, assembly, and/or test of the packaged device prior to shipment to the customer. A magnification between 1.5X to 10X is used to inspect for foreign material, contamination, illegible marking, damaged or bent leads, broken or cracked packages, defects in glass to metal seals, chip-outs to leadless ceramic packages and other defects which would interfere with assembly to the next level as shown in Figure 3.
JEDEC Std 9B is an industry standard that is also often referenced on package drawings as an external visual inspection criteria.
Figure 3 External Visual Inspection per MIL-STD-883 TM2009