For the person to learning an electron, the setting on circuit board checks a place (Test Point) is the work that does not pass in nature, for the person that but be opposite,learns machine, what is checking a place?

 

The goal that basically sets test site is to check the 0 component on circuit board to have up to specification and solder sex, want to check the resistor on a circuit board to have a problem for example, the simplest method takes avometer to measured its both ends to be able to know namely.

 

 

The each resistor that but be in large quantities of factories that estimate production,lets you measure each bat to go up with ammeter slowly without method, capacitance, inductance, circuit that is IC even is correct, had automation of so called ICT(In-Circuit-Test) to check the occurrence of machine stage so, it uses much root probe (say commonly for ” needle bed (Bed-Of-Nails) ” treat) the spare parts circuitry that contacts all need on bat to be measured at the same time, next by programmed control is given priority to with alignment, label complementary the character that means in proper sequence measures these electronic parts, all parts that test general board so normally need 1~2 only minute right-and-left time can be finished, the spare parts amount that inspects circuit board to go up and calm, the part grows more between a long time more.

 

But if make these bougie direct the electronic spare parts above bat of bring into contact with or it is its solder foot, very possible meeting is pressed destroy part of a few electrons, be just the opposite to what one wished instead, so clever engineer was invented ” the test is nodded ” , the two end in the spare parts are additional and derivative the bit of a pair of circles, solder was not prevented above (Mask) , the bougie bring into contact with that can let measure try out these bit, and need not direct bring into contact with those electronic parts that are measured.

 

 

Inchoate traditional plug-in unit still is above circuit board (the time of DIP) , the solder foot that can take a part really will regard as test site will use, because the solder foot of traditional part is enough strong, do not be afraid of pinprick, but classics regular meeting has bougie to contact situation of bad miscarriage of justice to happen, because general electronic spare parts passes wave crest solder (Wave Soldering) or it is SMT after eating stannum, in its the surface of soldering tin can form a stannum cream normally the remain that aids welding flux is filmy, this filmy impedance is very tall, the contact that often can cause bougie is undesirable, often produce the member that the test of the line works it is thus clear that at that time so, often taking air spray gun desperately blow, or it is the place that takes alcohol to wipe these need to check.

 

The test site that passes wave crest solder actually also can have bougie to contact bad problem. Later after SMT be current, the status that checks a miscarriage of justice got very big improvement, the application that checks a place also is gifted by big earth important task, the spare parts because of SMT normally very flimsy, cannot bear the direct contact pressure that checks bougie, use test site need not be used make bougie direct spare parts of bring into contact with and its solder foot, not only protective spare parts does not suffer harm, indirect also big earth promotes the reliability of the test, because the circumstances of the miscarriage of justice becomes little.

 

Do not cross the gradual progress as science and technology, the size of circuit board is smaller and smaller also, report should squeeze little ground solely above road board the electronic spare parts of next so much has had some took pain to, so test site takes up the problem of circuit board space, often designing end and between production end tug-of-war, after waiting, nevertheless this topic for discussion has an opportunity to talk again. Measuring pilot exterior is a circle normally, because bougie also is a circle, compare good production, let photograph adjacent bougie more easily also lean a bit nearlier, such ability can increase the establish needle density of needle bed.

 

 

1.Use needle bed will do circuit test to be able to have the restriction on a priori on a few orgnaizations, e.g. : The smallest diameter of bougie has certain limit, the needle of too small diameter breaks off easily damage.

 

2.The distance between the needle also has certain restriction, because each needle wants to come out from an aperture, and the back end of every needle solders again even a compressed cable, if the Kong Tai of photograph adjacent is small, besides the problem that there can be osculatory short circuit between needle and needle, the interference of compressed cable also is one big question.

 

3.On the side of certain tall part cannot establish needle. If bougie is apart from tall spare parts to too nearly can collision tall spare parts creates scathing risk, other external cause is a spare parts taller, treat the bed that provide an injection in the test even normally on starting a hole keeps away from, also cause secondhand cannot establish needle. The test of next contains harder and harder all parts on circuit board is nodded.

 

4.Because bat is less and less, check those who order number to put useless be taken time and again discuss, had had a few to reduce the method that checks a place to appear now, be like Net Test, Test Jet, Boundary Scan, JTAG. . The test method that waits for; to also have other wants to replace originally needle bed checks, be like AOI, X-Ray, but at present every test is returned it seems that cannot 100% replace ICT.

 

About the establish needle of ICT ability should want what the inquiry cooperates to manage a firm, the smallest diameter that checks a place namely and photograph adjacent check the least space of the dot, the least value that the least value that can have a hope more normally and ability can reach, but it is not more than how many bits OKer that the works chamber of commerce that has dimensions asks site of the least test and span of site of the least test leave, control an easy still damage otherwise.