DE10351720B4 - Test standard for testing optical detection systems used in SMD mounting and method of making same - Google Patents

Abstract

test standard for testing of optical detection systems used in SMD mounting, in which a carrier component (29) as a substitute for a substrate used in the assembly is provided, characterized in that elevations (13) as replicas of solder paste depots produced on the substrate in production at least with a cover layer (28) of the carrier component (29) together as one-piece molded part are formed.

Description

The The invention relates to a test standard for testing of optical detection systems used in SMD mounting.

Such also referred to as AOI systems (automatic optical inspection) Optical recognition systems are used in SMD technology (surface mounted device) u. a. after the production of solder paste depots on associated Contact pads for the subsequent Assembly of the SMD components used. Here are possible defects in the manufacturing process occurring during the application of the solder paste early be detected to incorrectly provided with solder paste printed circuit boards Weed out from the process before further for the faulty component Production costs arise. This takes into account the circumstance that the solder paste application on printed circuit boards in the SMD process the by far the biggest source of error forms.

Around the suitability of optical detection systems for monitoring the Lotpastenapplikation on printed circuit boards to determine and this to configure them so that they first have flawless solder paste depots recognize, it is common to use a sample of the circuit board in question as a test on the demonstrably no faulty solder paste depots available are (so-called "golden board "), for example several times in a row be subjected by the optical detection system, wherein a comparison of the exam results it can be determined whether the optical recognition system works reliably. Once the visual recognition system is configured, it can faulty solder paste depots by comparison with the geometry of the "golden boards ". How big the Deviations of defective solder paste depots from the target geometry have to be with it they can be recognized by optical recognition system can be do not detect with the above procedure.

Furthermore, according to the DE 42 27 667 A1 a transparent test plate is known, which has black markings on the top and the other side is highlighted white, so that the markings can be optically detected. According to the DE 198 30 474 A1 can also be used for optical detection test adhesive strips are glued to circuit board. According to WO 85/00885, also samples of light-scattering elements can be applied to a plate to calibrate a scanner.

The The object of the invention is to provide a test standard for testing specify in the SMD assembly used optical detection system which a comparatively reliable one Evaluation of the optical recognition system allows.

These The object is achieved by a test standard for testing solved by used in the SMD assembly optical detection system, at a carrier component as replacement for a substrate used in the assembly is provided, being surveys as replicas of in the manufacturing on the Substrate produced Lotpastendepots at least with a cover layer of the carrier component together as one piece Urformbauteil are formed. As a test plate so no with Lotpastendepots provided printed circuit board such. B. provided a "golden board", but according to the invention as a substitute therefor a one-piece trained test standard or a multi-layer test standard, in which the surveys made with the top layer in one piece are. This has the significant advantage that the Prüfnormal across from environmental influences much less sensitive, so it also defined over a longer period of time Conditions for a comparative study of the optical recognition systems to disposal provides. This also makes it possible Compare different optical detection systems with each other. For the Test normal comes a material used, which is a sufficient resistance with regard to possible deformations. Through this material Also the solder paste depots are being replaced because of their pasty consistency already in the event of an accidental contact while handling a ordinary Test plate like a "golden board "deformed could become.

For the test standard according to the invention it is advantageous that the carrier component or the top layer with the surveys made by the original method is. This is for the test standard made a suitable shape, so that advantageously a variety of test standards with approximate produced the same test parameters can be. Another possibility of Urformens consists in stereolitographic procedures in which the test standard directly in the liquid Starting material is generated.

An embodiment of the invention provides that the test standard is provided with layers that simulate the optical properties of a substrate printed with solder deposits. A coating of the integrally formed test standard has the advantage that the optical properties of the material from which the Prüfnormal is made in one piece, do not have to be considered. The optical egg Rather, properties are generated by suitable coatings of the different regions of the test standard, whereby these are selected such that the optical properties of an original printed circuit board with contact pads and solder paste depots are modeled as realistically as possible. For this purpose, the replicated Lotpastendepots can be tallized me, for example, with nickel and the replicated Kantaktpads with gold me. On the carrier component can also be applied a solder stop.

According to one Another embodiment of the invention provides that the surveys on the carrier component are arranged in groups such that the groups the solder paste patterns for typical, components used in SMD assembly. This can be advantageous the solder paste patterns on real printed circuit boards, d. H. configurations be modeled on contact pads and solder paste depots, so that by means of the test standard the optical detection systems under realistic as possible Conditions can be tested. The solder paste patterns can for example quad flat packages (hereafter QFP), ball grid arrays (hereafter BGA) or passive 0201 or 0402 devices.

According to one particular embodiment of the invention is provided that with the surveys on the support member defects in solder paste application occurring during SMD assembly are modeled. The targeted simulation of such mistakes has the advantage that the optical recognition systems to be tested also in terms of their ability can be examined to recognize typical errors occurring during solder paste application. requirement therefor is that the errors on the test standard are known exactly, so the result of the optical detection system in terms of a reliable one Error detection can be evaluated. For this purpose, the exact geometry of the test standard for example, on a disk which is used together with the test standard. A other possibility exists in it, a disk with the nominal data of the test standard to be provided with data that does not take into account the defined errors, but a theoretically error-free geometry of the solder paste pattern. By means of this data, an error detection of the optical recognition system during the examination of the test standard be provoked.

in the Following are various errors in the solder paste application described by the test standard can be reproduced. For the Case, that the test standard by molding a printed by means of stencils with Lotpastendepots printed circuit board is manufactured as well one way each shown how specifically by means of such a template said Error can be generated.

It is advantageous if as an error offset at least one Lotpastendepots on an associated Contact pad is modeled. This error occurs with the solder paste application on printed circuit boards, for example, when between the stencil for the Solder paste and the substrate is a tolerance-related offset. With a printing template, this error can therefore also be generated deliberately for the test standard be made by placing certain stencil windows in relation to the ones to be printed Contact pads offset in the template to be punched.

Farther It is advantageous if as an error only incomplete with Solder paste printed and / or a completely unprinted contact pad is modeled. This can be achieved if in the printing template for the test standard a stencil window, for example, with a passing through this Bridge is provided or a stencil window completely omitted becomes.

It is also advantageous if as a fault a bridge between two solder paste depots is modeled. This can be done, for example, with a stencil for creation of the test standard be achieved, with the two adjacent stencil windows on a Recess are interconnected so that when printing the Solder paste the bridge is printed, so to speak.

It is also advantageous if as a mistake in a solder paste depot a Volume deviation is simulated by the target volume. This one can be thereby generate, that in the stencil stencil window with enlarged or reduced cross-sectional area be provided, thereby increasing the amount of solder paste applied can be dosed.

Farther The invention relates to a method for generating a test standard for testing of optical detection system used in SMD mounting.

As already mentioned, it is usual Printed circuit boards conventionally produced with solder paste depots ("golden boards ") to use to test optical recognition systems.

task The invention is a method for generating a test standard for testing indicate an optical detection system used in the SMD assembly, with the test standards with can produce consistent properties.

These The object is achieved by a Method for generating a test standard for testing solved by used in the SMD assembly optical detection system, at a substrate component is provided with Lotpastendepots of the substrate component molded with the solder paste depots a negative mold in particular by micro-molding and in the negative mold, in particular by micro-molding the test standard is molded. This will ensure that from a first on Conventionally produced original of a printed circuit board with Lotpastendepots a negative mold is generated, with the help of a Variety of test standards can be molded, which is advantageous in terms of their geometry a high degree of agreement exhibit. Furthermore are the test standards produced in this way advantageously resistant against environmental influences, the properties of conventionally produced Test plates can affect. The method of micro-molding is suitable in a special way, because the finely structured, consisting of solder balls and binder surfaces Lotpastendepots can be mapped almost error-free.

According to one advantageous embodiment of the method is provided that the test standard as Urprüfnormal is used by that for the exam the optical detection systems more test standards according to the already explained Process are molded. This can be advantageous a very size Generate number of similar test standards, so that the investigation of optical detection systems also at a big one Number of potential users and over a longer period of time with constant Boundary conditions is possible and these results become comparable. Of the Urprüfnormal can namely Again and again an impression will be made, so that a Variety of molds for the production of the test standards can generate. This allows the extremely fine even with large quantities surface structures make the solder paste depot with high dimensional accuracy, so that due to the Oberflä chenstruktur the Lotpastendepots resulting optical properties with the manufactured test standards advantageous close to reality can be reproduced.

A Further training of the procedure provides that from the Lotpastendepots Molded elevations and / or Kontaktpadabformungen the test standard be coated so that the optical properties of Lotpastendepots or contact pads are modeled. Such Coating can for example be done by first a Mask on the test standard is applied, with the contact pads are steamed with gold can. Here, the Lotpastendepots are coated, which therefore due to their different optical properties by means of a second mask can be coated with nickel. Here are the contact pads covered so that only the solder paste depots with another Layer are provided, which covers the gold layer. The result is replicas Lotpastendepots on contact pads regardless of the base material used for the test standard the optical properties (reflection behavior) of the molded Have originals.

A Another embodiment of the method provides that the test standard on the side bearing the elevations outside the Kontaktpadabformungen with a solder stop layer is coated. This leaves Advantageously realistic the surface emulate the PCB, which in the SMD production regularly outside the contact pads with a soldering stopper is provided.

Further Details of the invention are described below with reference to the drawing described. Show here

1 An embodiment of the test standard according to the invention as a schematic plan view,

2 and 3 Elevations as a replacement for solder paste deposits on Kontaktpadabformungen as a schematic plan, the

4a to 4e selected process steps of the manufacturing method according to the invention for the Prüfnormal as schematic sections and

5 a section of an embodiment of the test standard according to the invention as a cross section.

On a test standard 11 according to 1 are different solder paste patterns 12a . 12b . 12c shown. The Lotpastenmuster consist, as shown in more detail below, from surveys 13 (see. 2 ) formed with a corresponding Lotpastendepots geometry. These are located on Kontaktpadabformungen 14 (see. 2 ), which correspond to the contact pads of an original printed circuit board.

The solder paste pattern 12a are intended for QFPs of different formats. Furthermore, solder paste patterns 12b for BGAs with different distances between the contacts. The solder paste pattern 12c are in 3 described in more detail. At the edges of the PCB are au In addition, optical alignment aids 11a intended.

The surveys 13 . 13a . 13b in 2 all have an offset 15 opposite the Kontaktpadabformungen 14 on top, leaving these over the edge of the contact pad impressions 14 protrude. Because of the offset 15 The elevations simu lated an offset of solder paste depots due to a tolerance caused staggered placement of a printing template on the substrate to be soldered, in which all Lotpastendepots are offset by exactly the same amount, a realistic geometry in the solder paste patterns 12a be brought about by all the surveys 13 at least one row 16 (see also 1 ) of Kontaktpadabformungen 14 of the solder paste pattern 12a be formed offset. Further through the surveys 13a . 13b simulated errors are explained in the notes to the 3 treated in more detail.

In 3 is one of the solder paste patterns 12c shown enlarged. It becomes clear that the Lotpadabformungen 14 are arranged such that these places P1 to P12 for 0402 devices 17 form on which the latter can be mounted. In each adjacent places P are the Kontaktpadabformungen 14 each arranged so that adjacent 0402 components 17 could be mounted offset by 90 °. Through the solder paste pattern 12c Thus, a geometry is provided which is suitable for testing the optical detection system in the presence of solder paste deposits for passive components with a large packing density, wherein in the solder paste patterns 12c (see. 1 ) Different grid dimensions for each adjacent Kontaktpadabformungen can be considered.

On the contact pad impressions 14 Surveys are designed with which different errors are modeled. The surveys 13 have no errors. The surveys 13c at P3 point in relation to that also in 3 shown xy coordinate system on an x-offset. The surveys 13d at P4 have a y offset and the bumps 13e at P5 have an offset in both the x and y directions. surveys 13f the adjacent squares P6 and P7 are still over a bridge 18 made of solder paste.

The surveys 13a at P9 are not fully formed. Similar defects in solder paste depots, for example, arise when solder material gets stuck in the stencil or the windows in the stencil are not completely filled with solder material. Last, the surveys show 13g P10 too low and P11 too large a volume.

In the 4 Selected steps of a production of the test standard according to the invention by the method of micro-molding are shown. According to 4a will be a first with solder paste depots 19 printed substrate component 20 on a firm surface 21 laid and with a casting resin 22 (eg UV-acrylate) in an appropriate amount. Subsequently, by means of a holding device 23 a glass plate 24 lowered onto the casting resin so that this the solder paste depots 19 on the substrate component 20 completely encloses. Because the glass plate permeable to UV radiation 25 is resistant to ultraviolet radiation sensitive casting resin can be cured in a subsequent step, so that on the glass plate, a negative mold 26 the surface of the substrate component 20 with the solder paste depots 19 arises.

In a second molding step according to 4b can the negative form 26 with the glass plate 24 together in the holding device 23 be inserted. On the pad 21 becomes a base plate 27 placed on the surface of casting resin is distributed. Subsequently, the negative form 26 the base plate 27 so approximated that the casting resin is the negative mold 27 fills while a top layer 28 and the negative forms of the solder paste depots 19 completed surveys 13 formed. By exposure to UV rays 25 the test standard thus obtained can be cured and removed from the generating device after curing has taken place. The test standard then has a carrier component 29 , consisting of base plate 27 and top layer 28 on, with the surveys 13 integral with the top layer 28 are formed (see. 4c ).

In the method step according to 4c becomes the test standard with a mask 30 covered in order then to steam the structures exposed in the mask openings structures with metal. In 4c is the vaporization of the surveys 13 with nickel along the indicated arrows 31 shown. Analogous to this can also Kontaktpadabformungen not shown in detail 14 (see. 5 ) are steamed with gold.

The production step according to 4e serves to coat the carrier component 29 with a solder stop layer 32 , For this purpose, a solder resist is applied over the entire surface to the test standard 11 applied and then through a photomask 33 so partially exposed that the areas outside the elevations 13 and the Kontaktpadabformungen (not shown) are cured. The arrows 34 indicate the incidence of light. Subsequently, the uncured components of Lötstoplackes be removed.

Of the 5 you can build the test normals 11 remove. The carrier component 29 consists of the base plate 27 and on this applied, formed from the casting resin cover layer 28 , With the top layer 28 the surveys are made in one piece 13 and also the contact pad impressions 14 produced by molding the substrate component 20 with the solder paste depots 19 (see. 4a ) in the negative form 26 (see. 4b ) are modeled. On the contactpad impressions 14 and the surveys 13 is a gold layer 35 applied. The gold layer 35 is in the area of the survey 13 continue through a nickel layer 36 covered. As a result, the contact pad impression appears 14 in a gold look and the elevation 13 in a nickel look, whereby the optical behavior of the original is modeled realistically. Furthermore, outside the Kontaktpadabformungen the Lötstopschicht 32 applied.

The survey also shows the surface structure of the solder paste depots, which is recognizable on average 19 on, wherein the cloud-like cross-sectional image is formed by the solder balls bound in the binder of the solder material. That in the 4a and 4b illustrated method of micro-molding of Lotpastendepots is particularly suitable for the impression of Lotpastendepots with sufficient for imaging the Lotkügelchen accuracy. Since these influence the optical behavior of the surface of the solder paste deposit, a particularly realistic appearance of the elevations can be generated by the finely structured replica of the solder paste depots.

Claims (12)

Test standard for testing optical detection systems used in SMD mounting, in which a support component ( 29 ) is provided as a replacement for a substrate used in the assembly, characterized in that surveys ( 13 ) as replicas of Lotpastendepots produced on the substrate in the production at least with a cover layer ( 28 ) of the carrier component ( 29 ) are formed together as a one-piece molded part. Prüfnormal according to claim 1, characterized in that this with layers ( 32 . 35 . 36 ), which simulate the optical properties of a printed with Lotpastendepots substrate. Test standard according to one of the preceding claims, characterized in that the surveys ( 13 ) are arranged on the support member in groups such that the groups correspond to the solder paste patterns for typical components used in SMD mounting. Prüfnormal according to any one of the preceding claims, characterized in that with the surveys ( 13 ) on the carrier component ( 29 ) in the SMD assembly occurring defects in the solder paste application are simulated. Prüfnormal according to claim 4, characterized in that as an error offset ( 15 ) at least one Lotpastendepots is simulated on an associated contact pad. test standard according to one of the claims 4 or 5, characterized in that as an error incomplete with Solder paste printed and / or a completely unprinted contact pad is modeled. Test standard according to one of Claims 4 to 6, characterized in that a bridge ( 18 ) is simulated between two adjacent solder paste depots. test standard according to one of the claims 4 to 7, characterized in that as an error, a volume deviation is simulated in a Lotpastendepot from the target volume. Method for generating a test standard ( 11 ) for testing optical detection systems used in the SMD assembly, in which - a substrate component ( 20 ) with solder paste depots ( 19 ), - of the substrate component ( 20 ) with the solder paste depots ( 19 ) a negative form ( 26 ) is molded and - in the negative form ( 26 ) the test standard ( 11 ) is molded. Method according to claim 9, characterized in that the test standard ( 11 ) is used as Urprüfnormal, from which further test standards for the examination of the optical detection systems according to the method of claim 9 are molded. Method according to one of claims 9 or 10, characterized in that of the solder paste depots ( 19 ) molded surveys ( 13 ) and / or Kontaktpadabformungen ( 14 ) of the test standard ( 11 ) are coated so that the optical properties of solder paste depots or contact pads are modeled. Method according to one of claims 9 to 11, characterized in that the test standard ( 11 ) on which the surveys ( 13 ) bearing side outside the Kontaktpadabformungen ( 14 ) with a solder stop layer ( 32 ) is coated.